All Wheel Drive Auto: Independent Seattle Subaru Service


Your Subaru Check Engine Light Explained

The Check Engine Light explained

Starting in 1996 all passenger vehicles and light duty trucks produced or imported for sale in the U.S. had to be OBD II compliant (On Board Diagnostics two). As well as meet newer vehicle emissions regulations. Part of this technology involves the check engine light or MIL. (Malfunction Indicator Lamp). While it’s true that prior to 1996 the check engine light did exist on vehicles, it took on an entirely new meaning and purpose in 1996.And this is where the confusion starts.

The check engine light comes on when the ECM (Engine Control Module) recognizes a malfunction with an emissions control device or an emissions control device monitoring system or if a specific condition is not being met. In many cases the vehicles overall performance won’t change much if at all when the light comes on, and is thus not taken seriously by the majority of car owners. But what the light represents is a potential failure in one or more of the vehicles systems that are meant to control the level of tail pipe and evaporative emissions produced to acceptable levels. In some cases the light can come on when the gas cap is loose. But the light can also come on when the catalyst system has failed.

Normally neither one will adversely affect the vehicles performance but both will allow the vehicle to excessively pollute our environment. The gas cap is meant to keep the fuel vapors sealed in the tank and evaporative emissions system rather then allowing the fuel vapors to enter the atmosphere as hydrocarbon emissions. The catalyst system is designed to lower tail pipe emissions to acceptable levels. These are just two examples of many possibilities.

There are essentially two types of OBD II Fault codes, conditional and component. A component code usually indicates a problem with a particular device, its circuitry or controls. A conditional code is set when a specific condition triggers the ECM to Command on the check engine light. Conditional codes are the hardest to accurately diagnose and repair and are typically the ones that do the environment the most harm. It is almost impossible to accurately diagnose and repair a conditional code with a code reader from a local parts house. It is simply not enough to have the code number but rather a thorough analysis must be performed by a qualified professional technician.

When a code is cleared, the emissions systems monitors are also turned to not ready status. It takes a specific drive cycle to return the monitoring systems back to ready status and the whole time the monitors are off they are not monitoring the emissions control devices. This is why sometimes a code can be cleared and not come back for weeks. Until the monitoring system is back to ready status the ECM doesn’t know about a device or a condition.

Specializing in Subaru repair gives us an advantage over other general repair shops when it comes to the diagnoses and repair of the check engine light and vehicle emissions systems on your Subaru. We will accurately diagnose the failure, any potential causes of the failure and keep you informed the whole way through. More importantly we can provide you with tips to help reduce the amount of emissions your vehicle emits and keep you an informed Subaru owner.

The above was prepared and written by.

Justin Stobb

Owner All Wheel Drive Auto

ASE Master Certified Technician, L1 Advanced Engine Performance Certified

WA. State Dept. Of Ecology Authorized Emissions Specialist


758 Responses

  1. Hey mate enquiry all the way from Oz. I found your blog and you have some great info here. I have a 2014 Diesel Outback 200,000km which has had DPF issues (expensive replacement) – it was going along ok but now have the situation mentioned here previously with the check engine light, cruise control light, traction control all on. You’ve explained already why these are linked, useful thanks, so my problem comes back to check engine light. Great local mechanic had a look but suggested more detailed diagnostics via dealership. Dealership (who I’m a little hesitant on) diagnosed EGR problems suggesting very expensive ($3k) rebuild/clean but “couldn’t guarantee” this would fix the problem. Spoke to an independent EGR/DPF specialist who (without seeing the car) said it may well be the problem and they could do it a little cheaper but still very expensive. A 3rd suggestion was to disable the DPF/EGR systems and be done with the problem. A couple of questions, is EGR a likely culprit for the warning lights being on? Is a full rebuild a reasonable proposition? Thoughts on disabling DPF/EGR?

    1. Hey Andrew,

      I have very limited experience with the Diesel in a Subaru as they were never offered in the US. I have only worked on a couple that were swaps. What I can tell you however is its almost impossible to diagnose a car without seeing it. You can only guess based on “pattern failures” Without knowing the possible penalties for disabling an emissions control device in your part of the world its difficult to advise you there. I also do not think you can disable without some sort of ECU rewrite which I will tell you is not feasible on the ECU in the Diesel Subaru without a second party software suite. If its gone 200k without issue, you might really look to repair what’s there and not try to reinvent he wheel.

      Hope that helps

    2. I didn’t know that Subbie even offered a diesel in other parts of the world, very interesting. With that being said like most diesels around now and days the emissions packages are made up of many different components depending on the build. The one thing they all have in common(mostly), is a ERG and A Diesel Particulate Filter, DPF. The DPF’s sole purpose is to collect particulate matter at the end of the exhaust, before the outlet pipe, muffler, resonator, tailpipe…ect. Think of it as a filter to catch what wasn’t burned off by being sucked back into the engine by the Exhaust Gas Recycler, EGR, or changed by other emission components such as a Diesel Oxidation Catalyst, DOC, which is basically a mixing tube in which things like raw fuel or Diesel Particulate Fluid are injected into the exhaust stream to burn off Particulate and alter the chemical composition of the exhaust stream to reduce NOX gases. So after the EGR, After a dosser plate, after a DOC chamber, you usually find a DPF which remember is a exhaust filter. Like filters they eventually get clogged up. Driving styles, chemical make up of the fuel you use, environmental conditions such as temperature, overall length of your trips, the type of your trips city vs country driving, how hot and for how long the Emission components can get all play a factor on how many Mi, K/m your emission components will last. Generally speaking, emission components for diesels need to get hot to do their job properly. That is why you see things like DPF Fluid, which is a chemical used to aid in the burning off of particulate.

      If you got near 300k Km on a single DPF I would say that is good especially here in the North East of the States I’m seeing DPF’s get clogged any where from 30k- 80k mi on our heavy Duty plow and dump trucks. However keep in mind this has a lot to do with idle time. Remember for DPF’s to function properly you need heat and flow. Sitting on the side of the road idling is killing these systems prematurely. So at 300k miles I would say it is definitely worth having you System cleaned, especially if you are experiencing the Subaru reliability. Personally I’m running a 2003 Subaru Outback 2.5 gas 4eat that I bought with internal engine problems do to lack of maintenance. Currently it is running my space engine that just turned over 310k miles on only a second set of HG. This engine is running the SIX Star gaskets among other parts I purchased from AWD Auto many moons ago.

      If you are up to the challenge perhaps you could save some money and take the DPF off and send it to a company to be cleaned/reconditioned. I imagine the $3k includes the mechanic costs for disassembly/reassembly. However, keep in mind this is only if your DPF is dirty. If you have other things wrong like a cracked or dirty EGR, or something leaking causing the clogging this would need to be diagnosed and repaired. I have seen before on some Diesel cars that leaking valves allowed excessive oil to enter the combustion chamber and get partially burned and then pushed into the exhaust stream, where the EGR got clogged up. At the end of the day I would open up the system and see what you have. If possible get and inspection camera in there and see what’s going on. $3k to get another 300k k/m vs $40-50k for a new vehicle, I would try to fix it. Cheers mate, from Buffalo

  2. hi Justin,the ambient and engine temp were the same @59 degrees fariheit when started the drive cycle, the scanner reads@ misfire monitor OK, fuel system monitor OK,comp component OK, catalyst monitor INC,heated cat NA, evap system monitor INC,sec air system NA, a/c refridge mon NA, oxygen sensor monitor INC, oxygen sensor heater OK, egr system monitor OK, taken from the scan tool, hope this helps,..thanks steve

  3. Justin, the o2 sensor,catalytic converter, and evap, and i will assume the purge and not the vent as it has no problem taking on fuel… the ambient was 59-60 degrees, and engine was cold, the 5/3 was to tell you that 5 monitors had passed the test and we were waiting for the other 3, 02 sensor-catalytic converter-and the evap hope this clears it up…thanks

    1. Do not reset or clear memory

      Try below for Catalyst.

      Start from cold. Let it run for no more than 2 minutes at idle. Drive it 45 MPH with the Transmission one gear lower than cruise for 5 minutes. 55 MPH for 10 minutes. Shut down and let cool until ECT values below 100 degrees (F).

      Start it up and let it idle for 10-20 minutes.

      If the 02 and Catalyst do not get to ready Status you must eval the 02 sensor and or circuit.


      1. I have a 2000 Subaru forester that has 4 engine codes p1100, evap emission control malfunction, knock sensor 1, and o2 sensor was just curious if these are all likely to be separate issues or could it be one issue causing it all I just bought the car a week ago

        1. Hey Mathew,

          Unless its a common ground issue or problem with the ECM it would be almost impossible for all of those codes be caused by one common issue.

          Look at the Knock sensor for a crack in it. Thats about all I can offer from here



  4. HEY JUSTIN, reaching out from the east coast on a 2003 legacy outback 2.5 auto with 380k on the clock, runs very well, cel funtions properly on startup and running, bulb WAS defective and replaced, but in almost 500 miles the monitors will not go pass the 5/3 to the next monitor[s] there is no cel in dash, no hicups, nothing, the approved drive cycle was preformed more than once and with a few variations, wiping the ecm clean with a hand held reader and tried again………any help would greatly appreciated,.thanks STEVE

    1. Hey Steve,

      Great mileage on your Suby!

      Which monitor wont reset? The 5/3 doesn’t mean anything to me. Generally speaking the Evap and Catalyst monitors will set last. Your better off not wiping the current data by clearing the ECM.

      What temperature is ambient and engine when you start out on the Drive Cycle?

      Knowing which monitor wont reset is key to trying to get it to monitor ready status.


  5. Hi Justin I have a subaru legacy 98 awd, throwing codes p0130, p0136, p0500, p1100, p1101, p1504, and codes p0130pd, p0136pd, p0500pd. I was thinking that with this many powertrain codes throwing, that it is more than likely the pcm? Thoughts on this?

    1. Hi Heather,

      While that is possible some time spent diagnosing a couple of those codes would prove that to be true.


  6. Hi Justin! Got an interesting one for you. I drive a 2005 Subaru Outback 123k miles. 3.0r with the 5eat trans. Always been very well maintained. The other day after leaving for a trip about 25 miles after departure (on the freeway) I got what looked to be a limp condition but oddly enough it didn’t limit speed. Just blinking sport light cruise light and cel. And no first or second gear from a stop. Felt like it was locked in 3rd. Upon bringing the car to my local(reputable) transmission shop to have it looked at they discovered two codes. P0700(trans malfunction) and p0758(shift solenoid b Circuit malfunction). They recommended a service and flush saying that Subaru’s for whatever reason are quite picky about dirty fluid. But added that this would be our first step in diagnosis since they would drop the pan. Surprisingly they said that everything looked normal no debris. Filters looked normal. Anyways I leave and 30 miles down the road same codes p0700, p0758. Only this time we have some additional codes. P0741( torque converter stuck off) p0420( bank 1 efficiency below threshold) p0345( cam sensor A circuit malfunction) p0335( cam sensor B circuit malfunction). What could be going on here? My first thought was a possible domino effect, if you will, of diagnostic trouble codes caused by one thing. So I went back to the beginning and had a look at p0758 solenoid b circuit. Removed my trans pan and ohmd out the circuit b solenoid. I got 6.7 ohms on every single one of my trans solenoids. No debris. Clean as a whistle. Could I have a bad tcm? Have you seen or heard of this before? Any help would be much appreciated.

    1. Hey Jay,

      I dont know why trans shops struggle so much with codes. The first step in diagnosing was locating the proper pins on the trans harness connector and conducting a Ohm test without ever removing the Pan. If a solenoid acts up when hot you are not going to see that after you let it cool and dropped the Pan.

      Sometimes when thew TC locks up and causes the Car to Stall it can falsely set the Cam codes.

      The original symptom sounds like a shift solenoid B issue.

      The last thing you ever, ever, ever want to do to a Modern Transmission when it has a Code set is Flush it. So no idea if more damage was done. It should have been diagnosed not serviced. I have no idea why that wasn’t done unless they tried to test and couldn’t duplicate, but saying the pan was clean when it has a code set is like saying your blood was a good color after a heart attack.

      The 420 is most likely set because the codes and thus the memory was cleared and the adaptive strategy was wiped out and now the ECM realizes the Cat Converter is no longer functioning as well as it should be.

      Where to go from here is a proper diagnoses. Which is exactly where it should have been day one, sorry


  7. Hi Justin,
    I’m looking for a little guidance with a problem I’m having with my 2012 Outback. I recently had the head gaskets changed and now I’m getting a P0028 error code. I have checked the operation of the Bank 2 Intake Valve Control Solenoid and it operates fine, the resistance value is 7.5 ohms, which is comparable to the Bank 1 side. I removed the IVCS just to make sure it wasn’t clogged, which it wasn’t. I had the timing belt and it’s associated pulleys and tensioners changed along with the serpentine belt, as well as a new water pump, thermostat, plugs and an oil change. The oil level is at the correct level. Any idea what could be giving me this code? If I clear the code, the CEL and other warning lights stay off as long as I don’t run the car to 3500 RPM. Any help would be greatly appreciated. Thank you.

    1. Hi Ken,

      When the HG were done most likely the switches were not replaced or the solenoids cleaned. I am trying to understand why the shop who replaced the HG doesn’t diagnose and repair it?

      Did you check the operation of the solenoid with the Subaru SSMIV?

      Ohm readings are kind of useless unless skewed.

      If you are not looking at live data o see what bank 1 and bank 2 are doing its going to be hard to diag. Could be a bad OP switch, there is one for each bank, thats how the ECM knows the system is working. Could be debris, could still be a solenoid issue.

      Thats about all I can offer


      1. Hi Justin,
        Thanks for the reply. I ended up changing the oil pressure switch which solved the problem. I took a reading from the connection to ground and it showed open.

  8. Hi Justin,

    Thank you for the blog post… I certainly agree working with a Subaru specialist gives me more comfort in discussing and trust when working on my car.

    That said, I wonder what your take/thoughts on my recent experience with my 2003 WRX wagon (170k miles) is with respect to how to get to a final diagnosis on my CEL issues.

    I and the shop I’ve been working with seem to be running out of ideas. It’s been tricky because it seems to be quite intermittent, but at the same time recurs consistently:

    – as the car aged past, say, 125k miles, I was starting to see random CELs… codes were from misfires through all 4 cylinders; could be from 1 or multiple cylinders, even all 4 at once sometimes; I would check them and clear them and they would intermittently come back in the same fashion within anywhere from 25 to a few 100 miles

    – one day (around 165k miles), on cold start in the morning, got on the freeway, moderate acceleration to freeway speed and the engine began violently shaking with almost no acceleration; persistent flashing CEL; got off the freeway immediately and stopped the car; had it towed to my shop

    – diagnosis: burnt valve cylinder 2; had a valve job done, that bank’s cylinder heads machined, etc.; car came back feeling great – power I forgot I had back, strong acceleration

    – now, I am again encountering random misfire CELs in the same fashion as before, but to make matters worse I am intermittently but also consistently getting flashing CELs; engine still feels strong and smooth to me.

    The only pattern to the flashing CELs I can discern is they are after relatively cold startups (first start in the morning after work, or first start going home after work) and seems to happen at freeway speeds around 60-70 mph, sometimes with light-moderate acceleration. If the CEL is not already lit, the flashing CEL doesn’t always leave a lit CEL, but I do get flashing CELs when the CEL is already lit.

    My shop at this point has swapped coil packs to see if there is a pattern, and swapped in different fuel injectors to see if it made a difference, but the issue persists and they are out of ideas. They re-did compression and leak down and didn’t see issues.

    Do you have any thoughts on the methodology for troubleshooting a relatively intermittent issue like this? From what I’ve read the troubleshooting process seems to be more of a trial and error exercise from quite a long list of possibilities…

    To me the car feels like it runs great, but I’m worried about longer term damage as well as what I do on eventual resale…

    Thanks for reading such a long posting!

    1. Hey Lionel,

      Assuming the WRX is stock, I would check to see if the valves are out of adjustment and should be checked cold, doesn’t matter if they were rebuilt yesterday. Another thought is the timing belt tensioner is not keeping proper tension on the belt until the belt itself warms up and stretches.

      Since changing coils, plugs and injectors does mot change the misfire what I have suggested is the most likely cause, it would not show up on a compression test either. Only other thing I can think of is an air leak @ the intake manifold, you did not mention if they conducted a smoke test on on your Subaru?

      Hope that helps


      1. Hello…I live in Elma WA. I have 97 outback sport 2.2 5 spd. I’ve been dealing with the 1507 code for some time (long). Initially I took it to the stealership and 100 bucks later tech said it was the throttle cable to tight. Drove back to Elma got off exit came to stop sign and light came on again then goes into limp mode. Did some research so I cleaned iacv, replaced NSS, knock sensor. And while I was at it replaced plugs/wires/pcv/coil/02 sensors and cats. To no avail. Bought a used iacv cleaned it installed still throws code. Car will start high idle slightly erratic and you can hear it missing/stumbling. Once warm it drops below normal warm idle and it’s missing but not terribly. I’ve had other people listen and they it sounds good but I can hear it for sure. Most of the time it runs ok but after 30-50 miles cel comes on then limp mode. I’ve also powerfoamed the entire intake system. My scanner only shows the 1507 code. I’m ok for transport as I have a tundra and just picked up a cherry 07 outback ll bean h6. But….love this little car and would like to figure it out and use it as my local hunting/fishing rig. It’s not the original motor and I believe it’s a 96′ motor but when it was swapped it ran great for many miles. Needless to say I will never take it to the dealership again and I don’t trust anyone local here. I know it needs a thorough scan but was hoping you might have something I’ve overlooked. Thanks for your reply. Based on your replies you seem to really care and that goes a long ways. Cheers!

        Nels Mikkelsen

        1. Hi Nels,

          Your post came in right as we hit are busy time and I am having a hard time trying to catch up with the website.

          Anyways so the 1507 is kind of a tricky code to diagnose without a real diagnostic scan tool like the Subaru Select Monitor 2 for that application. What I would be looking at is the the scan data that indicates if I am in “N” or in gear and any delay in the ecm recognizing I have moved out of gear into “N” or the opposite.

          We use to replace a lot of neutral safety switches for that code, and there isn’t a flow chart in the world that will get you there. The idle speed Control motor or ISC as its refereed to in manuals will control the idle speed differently when you are in gear VS Neutral, if the ECM is getting incorrect data about the status of the vehicle it will not operate properly and yes stall. Now I will add the 1996 ISC was also problematic, but there are tests to run to determine failure or if it just needs to be cleaned.

          This is where I would start, or you could make a road trip or throw it on your transport and we are happy to diagnose and repair for you.

          Hope that helps


          1. Thanks so much for the reply. What a crappy code to have lol. I read a similar post on a forum where he like me tried just about everything then replaced his fuel pump and that solved the problem. I can see why it’s termed a ” manufacturers code”. Also heard of bad grounds, alternator issues, etc etc. Anyway, thanks again.

          2. Nope none of that its most likely the switch and if you dont really know Subaru, you will never figure it out.

            Its a straight forward diagnoses if you know how.


  9. I am a first time AWD subaru forester owner. I want to ask a question and maybe it’s silly but I never owned an suv before. Am I supposed to put it in another drive when I drive very fast like on a highway? I am so scared I will ruin my little subaru. Last few days after driving on the highway it started to grind and sound like a small airplane. Not loud just the sound is similar? Am I riding it too hard? Last night my check engine light came on. All the fluids seem to be at proper level. What am I doing wrong?

    1. Hi Grace,

      Congrats on the Purchase!

      The AWD works automatically you don’t have to think or worry about a thing.

      The noise should be evaluated however just to be on the safe side, it kind of sounds like a possible wheel bearing.

      Hope that helps


  10. In my Legacy 2000 case, the CEL comes on regularly when I drive more than about 1 hour continuously. Since I drive mostly local, say 30 minutes ma, in hot and cold conditions, I can run more than a year with no CEL on, then on a longer trip the CEL will come on, I get it checked by my mechanic, code cancelled to see if it comes back and it stays off. Until maybe on the next long trip.

      1. Thanks Justin. The code has been “diagnosed” every time professionally and comes back as “evap code”. Mechanic stands there and scratches head after lengthy investigation. “Makes no sense” is the reply. “I’m going to cancel the code and we will see if it comes back.” And it does not. Emissions pass Ontario Drive Clean every time. Intermittent faults are the hardest to handle. I am the only person to click the filler cap into place and it is solid every time. Filler cap is perfect.

        1. Hi Colin,

          Let me come at this a different way.

          No I do not know everything that is occurring on your Subaru when this is happening, but I suspect that whomever is servicing your car may not understand how the OBDII system works, you should never clear the code and see if it comes back more than once. One time is understandable, but not multiple.

          If there isn’t a problem the light for an evap code will clear it self, I have tired conveying how the system works in several articles on the website, but it just doesn’t resonate I guess.

          When the light and codes are cleared, so are the readiness monitors, and depending on how you use the car please observe the following, It Could Take Months For the Monitors to go Back to Ready Status!! . So when you state the light doesn’t come back on for a while, most likely the EVAP System plain and simple is just not monitoring it self. The only way to know is to own a Subaru Select Monitor or true equivalent, and look everyday to see when the monitors go back to ready status, and if after weeks, the Evap Monitor is still not at Ready Status you will know why the code has not reappeared.

          I highly doubt anyone is smoke testing the Evap system for leaks, or testing the vent control solenoid, gas cap etc.

          You have a issue, which is easily repaired, a lack of real understanding coupled with many, (and I am not saying this is you) I am commenting about most customers just do not want to pay for the real testing required.

          Here is a snip it from the the State of Ohio Ecology website, I just picked a state at Random not knowing where you are from

          “If the repairs require the computer DTC’s to be cleared or a battery disconnect (which also clears DTC’s),
          then be sure to drive the vehicle for at least two or three days (older vehicles may take more time)
          including both highway and city miles. This will result in setting the OBD monitors to “ready” and ready
          for an emissions test. Unfortunately, when the DTC’s are cleared it turns the check engine light off and it
          is a guessing game as to when the computer monitors are “ready.” The generic drive cycle below may
          or may not be helpful but it will give you a better idea of what driving parameters usually need to be
          met. This may need to be repeated 2 to 5 times depending on the make, model and age of the vehicle.
          *Do this all at the same time and not in pieces (does not need to be exact)
          1. Let the vehicle sit for 8 hours
          2. Start the vehicle and let it warm up
          3. Drive for at least 10 minutes at highway speeds (55 mph or more)
          4. Drive for at least 20 minutes in urban traffic with at least 4 idle periods”

          Now I will add the letting it sit for 8 hours doesn’t mean a thing if the Temperature between ambient and engine do not achieve the proper values and if it’s started up and driven at say 30 mph for 10 miles everyday for three weeks, the monitor may not set.

          Now having said all this, if it is being properly tested and no leaks have been found, the only possibilities remain are either human error (you tightening the cap) or an issue with the monitoring system of intermittent function issues with a control solenoid or driver etc.

          I am not here to tell you that you must spend thousands to fix it, only that if it keeps coming back same code, there is an issue, but the method of diagnosing it needs to change.

          In closing, it’s really up to you, either you want to get to the bottom of it because you could be, and I stress could be venting raw fuel vapor into the environment (which is what the system is there to prevent) Or you don’t want to bother and because it’s so intermittent it’s not important, either way it’s really up to you, but there is something wrong, and it may need to go to someone else to get to the bottom of it?

          Hope that helps

          Thanks for the post


  11. Hi Justin, My check engine light came on while I held my car still using the gas on my steep driveway. I opened and closed the gas cap twice and the light stayed on. 2 days later I brought it to Subaru dealer to have it checked. They asked me what the problem was because the light cleared as I brought it into the repair place. I told them the check engine light was on, but it had cleared and they checked it out anyway since I had already signed the papers for repair. They charged $110 to check the code and after an hour they said I needed a Fuel tank pressure valve for another $120 plus labor so about $300 all together. Since the Check Engine light cleared itself, do I really need this extra valve replacement? Or are they ripping me off. I’m scheduled for the valve replacement tomorrow. Thanks in advance

    1. Hi Gerry,

      I just have no idea without seeing it.

      You should always ask for the Code number.

      If you don’t have a good relationship with the place you take your Subaru that’s the ting above all else that needs to be addressed.


  12. On a 2010 Subaru Impreza, the engine light came on at about 100,000 miles. From the mechanic, the oxygen sensor and catalytic converter need to be replaced. There is no change in performance. The bill is $2,600. Because the engine light is on, the all wheel drive is off and the cruise control is not accessible. What does an emission issue have anything to do with the access to cruise control and All wheel drive?

    Thank you for your time.

    1. Hello GG,

      Post 2005 all Subaru Vehicles are drive by wire (no throttle cable).

      For safety reasons any time there is any type of emissions, fuel, ignition or evaporative related systems issues the ECM disables the Cruise control and the Cruise Module then flashes the cruise control light to tell you it’s been disabled or there is a malfunction. Its just the way the software is written, they didn’t want to have to try and distinguish between which faults could pose an issues and which did not .

      Hope that helps


      1. Thank you very much for the quick answer. However, it leaves me perplexed.

        What safety reasons are we talking about?

        What are the risks with an emission issue?

        1. Hello GG,

          It would take me hours to explain theory and operation and then try and develop scenarios you might encounter. You having a failed Cat doesn’t create a safety issue but a check engine light and the protocol is to disable the cruise control whenever this occurs (the act of the check engine light being on) regardless of the reason why, so yes a loose gas cap resulting in a check engine light will also deactivate the cruise control.

          It’s really difficult to not repair a 2005 and newer vehicle again as other systems are disabled.

          Risks with an emissions issue? You have a system that is not functioning properly, it’s really up to you if you want to fix it.

          It can affect economy, longevity, the environment, and eventually clog and cause performance issues.



          1. Are all cars now designed that way (engine light on, cruise control off) or is it just Subaru?

            BTW, the Subaru with the fault is passing emissions tests. I am not sure what the passing criteria are, but it looks to me the wheels are not about to fall off the wagon. Are the Subaru criteria very tight to get the engine light on?

            I drove a 2001 Camry 180,000 miles with a cat and O2 sensor fault. I am sure it was not good on the engine in the long run, but by the time you are over 250,000 miles on a car, a lot of other issues come into play.

            Thank you very much for all your help and time, I appreciate.

          2. All cars that use drive by wire

            The tail pipe and check engine light have no correlation

            In many states the check engine light on is a automatic failure


  13. 01 Outback, standard 2.5 engine. Slightly over 200,000 miles…engine light came on, ran a check, code P0130. Changed upstream 02 sensor, used a Bosch…fixed problem, ran fine for one year, cel re-appeared. Check came back P0130. No noticeable engine issues, still ran like a top…ordered a new one (below) because I checked reviews on Bosch and found them to be not only cheap, but unreliable…

    Front Oxygen Sensor Denso 234 5003 Fits Subaru Impreza Legacy Outback 2000-2002

    Before the new unit arrived I took a short trip, about halfway to my destination engine started popping on lower revs, (accelerating out of corners or climbing hills) but ran fine
    at around 3000, turned around and brought it home, keeping revs high. Engine stayed in normal heat range for whole run, about 30 miles. Changed the 02 sensor. No difference, still missing and popping at anything below 3000. Ran check, came back P0130. Drove it to my mailbox about a half mile from my house (again, hi revs) engine light started flashing, stopped at the mailboxes, smoke pouring out from exhaust, which
    was very very hot…got it home quickly, engine light stopped flashing, ran code.
    Came back p0303.
    At no time in any of the above scenarios did the engine overheat. What puzzles me is that changing from Bosch to Denso caused the flashing cel and exhaust system melt down…The sensor and line plug were installed properly.

    1. Hi Eric,

      The problem sometimes with driving a car at all with a check engine light on and a malfunctioning sensor such as the front air fuel is it can cause the engine to run lean or rich at given times, which on an older engine can lead to catastrophic issues such as a Hg failure, or convertor failure, as lean = Hot. Components with over 200k can be easily stressed if they were already reaching service limits.

      Now I don’t know whats wrong with your car without seeing it, but I am just painting a picture of what could have occurred.


  14. QUESTION: My 2003 Baja has an intermittent problem. When I run it for a while the check engine light comes on and sometimes runs fine even with the check engine light on. At other occasional times, if I run it and turn it off for a few minutes or even an hour, when I start it again the engine won’t run right and misses with the check engine light flashing.The cat overheats then when I cool down the engine for several hours it starts up and runs fine. When this happens the codes 303 and 304 come on along with a code for cap loose or off, indicating 3 and 4 misfire. The last time it came on and ran fine but with the check engine light on solid code 420 came on again after a 50 mile trip. The car has been well maintained, has 127k and no leaks or overheating issues. Should I have it diagnosed by a dealer as regular mechanics can’t find the problem. I bout it used and it appears the cat has been replaced along with coil pack, wires and plugs, possibly front o2 sensor. I am in PA and it passed emissions inspection in November after my mechanic got the check engine light to go off. This intermittent problem is difficult as it won’t miss when I take it to the mechanic. What should I do? Great site and info but I don’t want to guess at the solution and just start replacing parts. I love the truck.

    1. Hi Steven,

      The best option is to find a Independent Subaru shop for the diagnoses. Second option would be the Stealer if you can’t find a good independent.

      Letting the vehicle misfire can damage the convertor.

      You can’t drive a vehicle that overheats, it must be fixed. Its possible the misfire is an internal HG issue.

      Hope that helps.


  15. I have a 98 Subaru legacy all of a sudden it started acting up n the check engine light came on took it to get checked they said. Speed sensor & p1540 so does that mean its both or is the p1540 what’s wrong with the sensor or what?

    1. Hi Sara,

      It would need to be diagnosed, there is no way from here I can know if the Speed Sensor is faulty, only through testing will the answer be known.

      Doesn’t do much good to suggest to you the sensor is faulty only to find out the wiring is faulty.


  16. My heat/ac blower stopped working in my 2004 forester X a couple weeks ago. I haven’t had it fixed yet but today while I was idling, my temp gauge started to rise and my check engine light kicked on.

    Upon my own inspection, the wiring running to the blower motor is melted and has melted into the connector.

    My coolant is a tiny tiny bit low but nothing alarming.

    Do you think these two issues are related?
    Would the blower motor issue trigger a check engine light?

    1. I can’t really see how they are related

      Obviously the fan motor and the wiring, must be taken care of.

      But the check engine light needs to be diagnose as does the cause of the overheat.


  17. Hello,
    My basic question is: how long show I wait before I have peace of mind that a check engine light will not come on again due to the same problem?

    Background: I have a 2013 Subaru Impreza. At 23,000 miles the CEL-non-flashing- came on with code POOOC (Bank 2) Camshaft Position Slow Response. My trusted Subaru dealer replaced the LH Intake Cam Sprocket, Front timing Cover and some Oil Rings.

    Less than 20,000 miles later-same code comes up. This time, my trusted Subaru dealer has now been sold. New dealer said all I need are O-Rings, something called an OCV but no cam sprocket. The items noted above were replaced. It has been over two weeks and the check engine light has not come on, but I am suspicious as I had the car into another shop (not Subaru) prior to the dealer repair and they diagnosed the problem as needing the same part as my original dealer called for the first time the CEL came on.

    I am concerned that I’m driving the car around and there could be engine damage in the meantime. Also, if this is the same problem arising twice in 40,000 miles, do I consider getting rid of the car? I had two Legacies before this and had almost maintenance-free experiences with them. Please help!!

    1. Hi Cathy,

      That’s tough to answer, But the repair should still be under the year 60,000 mile power train warranty. I guess let the dealer replace what they are suggesting under warranty and take it from there.

      The O-rings are just a required item when removing the front timing cover on the FB series engines, and its tough to know exactly whats wrong without removing the chain cover, which is very labor intensive.

      Hope that helps and I am sorry your having that issue this early.


  18. I’ve got a 2004 Subaru Legacy Outback that needs to pass state inspection in Massachusetts. Just had some work done to the vehicle, including emissions-related work due to a P1443 engine fault code that has now been cleared as of yesterday. What is required before the car is ready to be inspected for emissions? How much time or mileage? How many engine starts? I need to get inspected by the end of this month, so the timing is tight.

    1. Hi Gary,

      There is no black and white answer to that question. One car could be done with one 45 minute drive, the next could go two weeks without having all monitors at ready status.

      It’s about drive or warm up cycles. The best way to know is to have it scanned for readiness monitors at ready status prior to the test to know for sure.


  19. hello, l have a subaru legacy b4 2004 model. lts misfiring, and l suppose the company which did diagnosis didnt do it well, they said its primary and secondary ignition coils. is that so, but the car still drives. i thought if they were primary and secondary ignition coils, the car wont move. is it safe to drive, l have to drive to 300km to a better comapny. lm in Mozambique, need to drive to zimbabwe

    1. Hello Watson,

      So you have 4 coils, and if one has failed it will run but very poorly, and no it shouldn’t be driven until you can afford to resolve it.


  20. Hello Mr. Stobb,

    Just found your amazing site. Please, would you kindly help!

    2005 Subaru Forester 69K miles. No problem until now. Don’t know anything about cars other than driving very short distance to work; since retiring 2 years ago, only drive very few miles to shop or to doctors. Two months ago, CEL comes on but steady with flashing CCL. Diagnostics scan at NJ Subaru dealer returned Code P0851, replaced neutral safety switch indicator. Lights off, Brought car home, lights on again. Back to shop. This time also mentioned that car hesitant to start – did throttle body service to fix. On the CEL and CCL, scan showed new code P0852, re-adjusted switch. No lights on short road test. but lights came back on. Recommended change ECM and may require wiring adjustment.
    However, they also said that if the expense is a bit much for me, it was ok to continue driving the car with the steady CEL and flashing CCLwith the minimal driving that I need. Is this correct? Would appreciate very much your kind advice.

    Thanks so much,

    1. Hi Janet,

      First of all thanks for the feedback, second of all thanks so much for having the code numbers, because in this case the fact that you have the code numbers means, I can tell you exactly what is going on!

      So P0852 pertains to the Neutral safety switch. The P0851 was the park switch, so you must have an Automatic transmission in your Forester.

      While it’s somewhat true to say it’s okay to drive with a solid check engine light and flashing cruise light, this also may have been the cause of the hesitation when starting, that may pop back up. The problem with leaving the light on (besides you paid to have it sorted out) is that you will never know about something new.


      The issue is the inhibiter switch is out of adjustment, it contains both the park and neutral switch within it. They are finicky to adjust, but that’s what needs to be done, and it should be on the dealer. The P0852 is setting because the ECM, or TCM incorrectly thinks it’s in Drive or Neutral, when it’s in the opposite. This is actually very common, so common that Subaru issued a service bulletin #16-68-06.

      The Dealer simply needs to reference that bulletin, adjust the switch as per the bulletin, and you should be all set.

      Glad I could help


      1. Thank you so much Mr. Stobb! Apologies for this late response. I was away with no internet access

        I’ll to back to the dealer sometime next month; will give you an update. I just wish you had a branch in NJ.

        Happy New Year!

      2. Happy New Year Mr. Stobb,

        Thanks so much. Again my apologies for the late response. I was away with no internet access

        I was going to bring the car back to the dealer today, Jan 2nd, to have them do the service per service bulletin #16-68-06 like you advised. I did not go because the CEL started blinking. What now? Please would you kindly advise. How I wish you had a branch in NJ.

        Thanks again,

        1. Hi Janet,

          With the CEl Blinking, that’s a tow it in kind of a thing. That’s my best advice, and I know that’s not fun to read


          1. Hello again Mr. Stobb,

            Definitely “not fun to read” but thanks so much for taking the time to respond! I wonder what the dealer will come up with this time; I’ll most likely give you an update.

            Thanks again.

          2. Hello Mr. Stobb,

            I had wanted to get the car towed to the dealer two weeks ago. But when I started it, the CEL was on, but was not blinking. Drove around the block and CEL remained steady. Been driving a lttle – mile drives to doctor, church, grocery. So far so good – CEL on, but not blinking.

            You had advised to have the dealer fix the inhibitor switch per service bulletin #16-68-06. Is this really, really necessary? What if not done? Am concerned about having to go back to the dealer – they seem to do quite a bit of work to increase charges, and yet not fix the problem. Like I spent a lot for their work on the CEL, but not fixed in the end.

            Mr.Stobbs – thanks ever so much. You are very kind to extend assistance to anyone who asks for your help.

          3. Hi Janet,

            The TSB should result in a net Zero Charge to you, and yes it needs to be done..

            You might need to call SOA ( Subaru Of America) 1800 Subaru 3 If the Dealer does not want to play nice.

            Hope that helps


  21. Hi Justin,
    We have a 2005 Subaru Impreza. Recently ran out of gas on the interstate (blame my husband:) ), and about ten minutes after we’d got going again the check engine light went on. Are the two related? (Sorry if this has already been posted, I got about halfway through reading all the posts…)

  22. Hi justin I have a 2001 Subaru legacy have been getting the check light . My mechanic checkd error code said was cam shaft sensor which I got replace but stil got Ecl coming on so I got it replaced again but problem still continues. I have notice that it only lights up and car starts shaking as if it’s loosing power when I have lights on or worse if im at the stop light plus have noticed also while driving putting my windows put or down car strts to shake and Ecl will light up. I have changed my battery, spark plus and oil filter changed still no luck pls help

  23. Hi Justin…I still have my ’99 Forester about which you advised me years ago and after I bought your headgasket kit had no problems until this week (July 2015). You might be wondering why I am writing with regard to CEL issues. My problem stems from an Avital entry and remote start system that was in the car when I bought it. It was always loaded with bugs that would prevent me from starting the car or locking myself out…Recently my wife took the car and later that day she was unable to start it…the anti-theft feature was
    the “bug” of the day. My wife had a friend’s husband search for the button that allows
    one to kill the anti theft so the car can be started. He messed around and I had to make the emergency trip to get the car started and she told me he had changed some wires. I was able to get the car going but the CEL flashes rapidly ALL the time and none of the features work on the AVITAL system. I called the guy and he made up some story that he had left the wiring the way he found it. Now I have no features and I am worried that if a “Real” issue comes up with the car I will have no way of knowing..That’s my CEL dilemma. Thanks. Tom Lever Vermont

    1. Hi Tom,

      I am just not familiar with the aftermarket system you have, and it sounds to me like it needs to come out.

      That’s what I would suggest is to remove the aftermarket system, and if you still need those features you will need to look for a new aftermarket system.

      Hope that helps


  24. Hey Justin,
    I’ve recently purchased an MY05 Subaru Impreza RS 2.5L 160,000km and the CEL comes on and off regularly when i’m driving. I’ve taken it to supercheap auto (from australia) to get a scan and it showed code 22 Knock Sensor 1.

    Being in our compulsory 3 month used car warranty I contacted the dealer (who is also a mechanic) and he was sure that it was no big deal. He said it will almost always do that and to put some high octane fuel through and it should go away. Ive out 98 in and it’s still coming on and off.

    Should i trust the used car dealer and leave it or insist on a replacement knock sensor while under warranty?
    Thanks mate

    1. Hello Julian,

      The knock sensor is a common component to fail over time on a Subaru. In the U.S. you wouldn’t have much of a leg to stand on in terms of a warranty on a used car, but I have no idea the rules in Australia. A good Dealer would probably help if it was a right away kind of a thing, but there is still no guarantee. In the interest of saving money however it’s always worth asking the question.

      It’s not an expensive repair here, but again I just don’t know pricing in your country.


  25. Great site! I have a 2008 subaru outback that I have an oil change on every 3,000-3,500 miles. The night before last, it was parked outside and we had a lot of rain that night. The next morning I start to drive it and it has inconsistent gas feed, at one point basically no acceleration. The engine light was flashing. I manage to get it around the block and back home. I pull it into my garage and after about an hour go back out and start it up. The engine light is off and is drives fine as I take it into a mechanic. He hooks it up and finds that cylinders 1 and 3 had misfired. He then clears the codes. Since the car is running fine, he suggests I use better grade fuel, and use ‘heet’ once monthly. Today, I drove to a town about 45 miles away, and on the return trip the engine light comes on and stays on, although I don’t notice any performance issues with the car. Do I take it in for repair, or do I play it out and see if I upgrade the fuel and add ‘heet’ if that makes a difference. Any suggestions welcome! Thanks!

  26. I have a 2008 Subaru Outback. After it sat outside the night before last (and there were heavy storms), I lost acceleration when I went to drive it the next morning, and the engine light was flashing. I managed to go around the block and return home. I pulled it into the garage and after about an hour I was able to drive it to the mechanic and the CEL had gone off, and there were no problems. I took it to a mechanic who hooked it up and said that the first and third (same side on the left)cylinders had misfired. Since there hadn’t been a problem on the way to the mechanic he said to add ‘heet’ to the tank and change to a better grade fuel. So this morning I drove to another town about 45 miles away. On the return the engine light came on and stayed on, although there were no discernible problems with car performance. I have not yet added anything to the gas or had the need to get gas, so have not done those things. Should I return it to the mechanic, or wait it out while using better gas and adding the ‘heet’? Any suggestions?

  27. My check engine light came on and won’t turn off after I had my head gaskets replaced at the local Subaru Dealer. I have a Forester 2002 with 115,000 miles on it. (This is the second time the dealer has replaced my head gaskets and I get my oil changed every 3,000-4,000 miles)
    I took my car back to the dealer who told me I had a failed catalytic converter. I’m suspicious since I never had an engine light problem until 2 weeks after the head gaskets were replaced and I htink the tech just hooked it up to the computer.
    Is there a reason a head gasket replacement would cause the check engine light to come on and how do I make sure this really is the catalytic converter?

    Thanks for your info…
    How much do you charge for diagnosis for a check engine light….

    Thank you

    1. Hello Sue,

      We would charge between $67.50 and $109.00 to perform a diagnoses of the catalyst function once we had scanned it and knew that was the code, if we made repairs to it we would discount or waive the inspection charges.


  28. Justin,

    Thanks for providing this great service. My question has to do with my daughters 2005 Impreza. The check engine light comes on/cruise control flashes etc. It was diagnosed by my usual mechanic and a Subaru dealership mechanic (to the tune of $115). Both say it is a problem with the fuel tank pressure sensor, and it needs to be replaced. Can you tell me what the long term affects of not replacing this sensor could be? Does it matter that my daughter is moving to Arizona in a month? Also what does the replacement part typically cost? How long does it take to repair? Thanks again.

    1. Hi Joe,

      I am confused as to why the Dealer or independent wouldn’t have already given you prices locally? I would call them and ask for an estimate. As far as not repairing it, It wont pass an emissions test required in AZ to license the car if that is applicable to your situation and the light can’t come on to notify you of anything new as it’s already on, most of the time that wont present an issue, but in some cases there would be no warning before leaving your Daughter stranded. This is not an expensive fix, and I would want my daughter safe.


  29. Justin,

    My daughters 2005 Impreza has had the check/engine light- cruise control flashing as mentioned by others. I brought it to a private mechanic and a Subaru dealership. Both diagnosed the problem: the fuel tank pressure sensor needs to be replaced.

    What is the long term affects of not getting this repaired?(other than no cruise control)My daughter is moving to Arizona next month and I want to make sure she has a safe car. Also how much does the part cost, and how much labor is involved.

    Thanks so much for providing this great service.


  30. Cruise light flashing – check engine light on…..usually it is just that the gas gasket needs tightening. Pop lid open turn gas gasket to remove from car spout. Wait a second or two and replace gas gasket and turn gasket until you hear several clicks, usually about three, four or five clicks. Close lid. Problem usually solved. This will happen if you recently filled your car with gas; later in the day your car will have a check engine light on and a cruise light flashing.

    1. Hi Sue

      Thanks for posting.

      That only works if you leave the gas cap loose and that causes the light to come on, if the gas cap isn’t loose and the check engine light and cruise flashing are for a failed mass air flow sensor for example trying to tighten the cap will not yield any results, that’s why I suggest you own a simple code scanner and scan the codes first, if it’s a P0440 or P0457 tighten the cap and go from there, if it’s something else don’t bother with the cap.


  31. Hi. 1996 Subaru Impreza sedan, 2.2L engine, been trying to get the check engine light off, new plugs, plug wires, coil, and CPS. No progress, light keeps coming back on. Flashes sometimes while driving also, sometimes stays on solid. What’s going on?

    1. Hi Jon,

      It’s unwise to attempt the diagnose and or repair of a 1996 and newer vehicle as it pertains to a check engine light with out first performing a code scan. I have no idea what could be wrong as I would need at a minimum the code or code numbers to be able to even form a potential course of action.

      You can replace the plugs, wires, coil, and even the entire engine, but if it’s a fuel vent solenoid code for example that’s on the fuel tank and your no where close to fixing it.

      My advice is to buy a code scanner, get the codes and go from there.


  32. we have a 2002 Subaru legacy outback with 250,000 miles on it we replaced water pump, timing belt ,plugs,plug wires,fuel filter but when we try to take off sometimes it wont go the rpms wont even raise with it floored it asks like its not getting fuel than we take foot off pedal and try again and its fine it onlys happens sometime times what could be the problem

    1. Hi Billy,

      You did not indicate if the car was acting up prior to the repairs you made, or if its just been since it was serviced?

      As far as what could be the problem the list is long and requires a diagnoses of some sort to know whats wrong.


  33. Hi Justin,

    You have an awesome, informative website here… thank you so much for all of the time and effort that it takes you to mantain it.

    I have an ’03 Forester 2.5X with 91k. It drives and behaves perfectly, no CEL, etc.

    There is one issue that has me troubled. however, and I was hoping that you’d be able to point me in the right direction.

    The transmission ahifts perfectly on its own, including downshifiting (lower gear and higher rpm), and upshifting (higher gear, lower rpm), and shifting from any one gear to the next. When I use the cruise control, it works perfectly, engages on the first try, maintains consistent speed, and resumes speed correctly. When set, the cruise control downshifts (to get up a steep hill) on its own, but for some reason it does not upshift once it has cleared the hill and is on flat ground. The second I turn off the cruise control button, the car upshifts as it should. When I am driving on that same identical section of road, and not using the cruise control, the car dowsnhifts perfectly to get up the hill, and upshifts perfectly once I’ve cleared the hill.

    I also have an ’03 Legacy that runs/works perfectly, and shifts perfectly both with the cruise control on and off. So I know how the cruise control should work with that engine and transmission, since they’re the same in both the Legacy & the Forester.

    Thoughts? Comments? Very wise/helpful suggestions?

    Thanks so much,

    1. Hello Rich,

      So really the place I would start if i was trying to track that down would be to look at requests and commands using the Subaru Select Monitor or equivalent. As well as data inputs if there was no command to up or down shift, its possible load data or speed is being misinterpreted by a module. If the request is there but no command that would indicate an issue with a ECM, TCM or Cruise Module.

      Its possible to trace down but data is the starting point for something like that. I will also add I have encountered a few 2003/2004 Foresters that had some weird symptoms, but not exactly as that you are describing, post software updates, that required replacement of the ECM.


  34. Justin your site has been very informative thank you for your time in answering everybody’s questions now i have a very common problem it seems but the cam shaft seal went out on our 2002 outback legacy 2.5 so we replaced it along with the timing belt ,timing belt tensioiner, water pump , thermostat, plugs , plug wires , crankshaft seal and oil filter . seems we had it opened up in front seemed like a good time to do all that , now after running it about 50 miles the CEL came on i know its the P0420 code we know its the downstream o2 sensor as we found out the used car dealer ship we got the car from cut the wires to it for some god awful reason so now with all that info here comes my question is the downstream o2 a four wire or three wire and when we drove it about 150 more miles the CEL came on flashing than just stayed on had it checked and all four cylinders misfireing .What could be a good starting point

    1. Hi Billy,

      I am having a little trouble following you post. I get the cam seal leak and the corrective action. But than we had a P0420 set and the diagnoses was the rear 02 sensor? You are wondering if the rear 02 sensor is supposed to be a 3 or 4 wire type sensor but still somehow now have multiple cylinder misfires.

      You have given me no code numbers so I can only assume its setting P0301, 302, 303, 304 420?

      The place to start is diagnosing the misfires, as it cant be driven in that state. The 420 may be related to the misfires and a secondary issue or it may be the converter is failing as well.

      I wouldn’t assume the used car dealership cut wires, it could have been long before they saw it, and there is little chance they inspected anything to know there were wires cut? It’s curious that its not setting a code related to the rear 02 sensor if the wires are in fact cut however. Should be a four wire heated 02 sensor.


      1. sorry those were the codes it thru for the misfires and the P0420 was thrown before the cam seal went out and the CEL only flashes when we accelerate but as for the cut wires after we bought the car we found a jumper wire on the front o2 sensor after i pulled it thats when i noticed the cut wires and also when the code was thrown for the o2 sorry for leaving that out

  35. Hey Justin, wish I lived near your shop as I also have an 05 Outback and the Cel came on shortly after we bought it (used 125,000 mi) and our original mechanic replaced an o2 sensor, cleared the codes and the cel came back on in a couple days, brought it to a more thorough mech who said a bunch of codes came back including the o2 sensor again, and one indicating that the fuel was burning “rich”- he checked each of the sensors and determined that they were working and that the only thing that looked remotely worn were the spark plugs. Swapped them out and a week later cel back on and flashed for the first time this morning..the car hasn’t ever run that great since right after we bought it- and the mech said he noticed that it hesitated under load- this last cel came on right after my wife filled up with 85 octane ethanol free gas and most people I talk to are saying 87 is the best- could it be that simple or anything else that sounds familiar without the specific codes? Thanks D

    1. Derek,

      Sorry you are having the trouble you are but like I state all the time here, unless you give me the specific codes that are being set when the check engine light comes on there is nothing I can do from there.


  36. I have a 2006 Forester. CEL light came on with flashing Cruise. Car had rough idle and ran rough at low speeds. took it to dealership travelling on highway – car ran great.
    Dealership said codes were:
    P0301 Cylinder 1 Misfire Detected
    P0302 Cylinder 2 Misfire Detected
    P0303 Cylinder 3 Misfire Detected
    P0304 Cylinder 4 Misfire Detected

    Dealership could not diagnose further as car was running fine.

    They suspected that it was the EGR valve and they would start by replacing it.

    Every Forum I visit and look for posts about EGR valves and CEL are due to P04xx codes and not the 301-304 I have.

    I have no confidence in the dealership when they can’t diagnose a problem and just want to start throwing parts into it.

    So questions:

    1. is this a legit solution to the codes?
    2. the car is running fine now – will the CEL reset itself if all continues to be fine?

    1. Hello Kardinal,

      Id like to start out with trying to explain there is no way I can factually know whats wrong with your car, only try and paint a possible picture for you.

      So when the EGR fails in a way that the ECM can recognize it will set a EGR related code, when an EGR becomes faulty in a way that does not create data back to the ECM to trigger an EGR related fault but instead the ECM has only picked up that there is a misfire or in your case multiple misfires then yes the EGR could be at fault with out the ECM ever knowing it, that’s when only a skilled and trained technician can diagnose whats the matter with your car.

      “I have no confidence in the dealership when they can’t diagnose a problem and just want to start throwing parts into it.”

      Sometimes issues with cars are complicated and it sounds like thats the case with your car with the current situation, if it was going to be easy Techs would not be needed.

      All a tech can do is look at items that could cause multiple misfires and test until he finds something that is not working correctly, in the case of the EGR the theory would be that it stayed open at idle when it should have been closed, causing a massive internal vacuum leak and lean condition where the amount of air coming in was greater than the ECM knew about so the air fuel ratio was incorrect, the burn in the cylinders weak as a result and the misfires thus created.

      This can happen, we have seen it and Im sure the Dealer has as well the reason they have used the term suspect, is the car is not acting up now, thus they cannot “prove the theory” The marketplace does not allow for this, no one would like to pay for extensive testing until theory is proved like in a scientific study, but alas that is the position we find ourselves in sometimes as Techs.

      Your choices are let them do the EGR, or don’t. Try something or wait until it not just happens again but is occurring during testing, because until it is tested during the period of time that it is acting up its only a theory and you want facts. It may have been a pice of carbon held open the EGR for a while then became dislodged and it doesn’t happen again.

      Most of what you read on forums is not entirely accurate for every situation.

      The light may go off on its own after some drive cycles with no faults.

      Hope that helps


      1. Thanks Justin, you provided an answer in a way the dealership service manager couldn’t – hence my skepticism with them.

        I appreciate the time taken to answer.


  37. I have a 2006 my06 subaru impreza non turbo and my Check engine light comes on with the code p0851 neutral switch
    how do i find where that is and how do i fix it

  38. One last question:

    When I was young, in the winter, we were supposed to sit and let the engine warm up. But I was told by a mechanic that this is no longer necessary. Yesterday, I felt I should sit and warm up the car but then I thought that it would only add emissions to the atmosphere for no reason.

    So now I’m wondering if that mechanic was wrong: Do cars still need warming up? And if they do, what’s the criteria?

    Thanks in advance.

      1. Justin thanks for your reply – it was about 12 degrees, the car is an 04 forester and it was going to go about 10 miles or so at highway speeds.

  39. Hi. We have an 04 Forester and we’ve maintained it faithfully.

    We’ve had extreme freezing temperatures here in New England and yesterday my car did not start immediately, as it usually does. It took a few start/fails to get it going and remain on. This is unusual but I assumed it was the cold (was about 12 degrees). I didn’t notice a CHECK ENGINE light then or later when I started it up and drove home.

    But today, again a slow start although not as slow as yesterdays, I noticed the yellow CHECK ENGINE light was on and remained on. It was still on when I started the car an hour later and went home.

    What do you think this could be? Best/worst case scenario? (this couldn’t come at a worse possible time)

    1. Hello Cy Cy,

      The light could be on for anything from a loose gas cap to a failed convertor.

      Costs? Well a good shop would clear the light and talk to you about making sure your gas cap is tight for free, this would be a shop you have a relation ship with that doesn’t nickle and dime you that would be the low end of things, a Convertor can cost as much as $1500.

      The only way you will know is to have someone at a minimum scan the Car and report back to you the codes, from there it may need to have a diagnoses performed.

      I wouldn’t let it stress you out there is a reason the light is yellow not red. But you will need to have it looked at if you don’t own a code scanner, without knowing at a minimum the code there is no way to to advise you about anything factually only speculate.


  40. My 2002 LL Bean 6 cylinder now has the CEL on, and on occasion it will flash (around 5 seconds) then goes back to solid. Why would it be going from solid to flashing randomly? If it was misfiring, would it be constantly flashing?

    Very frustrated

    1. Hello Jet,

      A flashing check engine light means one, the car is misfiring at the time it’s flashing, and two, please don’t drive me anymore until you fix me.


  41. Oh, and also, all my fuse are OK, in Eng. Comp. and L.H. Dash.
    I have two questions:
    (1) What are the two hidden fuses under the fuse block behind the Drivers side dash ashtray? You can’t remove them but you can just see them. They seem to be on the back of the Code reader plug housing.
    (2) Above the gas pedal, there are three wiring connectors not connected to anything: The green 2 wire connector actually is damaged. I see one wire is pulled out of the back of it, pink color? The other two are white connectors, a 4 and a 2 wire conn.
    I looked under the pass. side dash for that Green connector mentioned in the forum and I don’t see it (should it be near the heater?) where should I look, to see if it is wrongly connected all these months?
    Thank you for this forum, I have learned so much. I will not re-boot the computer by removing Batt. cable or anything until this problem is fixed or properly Diagnosed by someone!

    1. The wiring under dash are D and U check connectors used to activate solenoids and relays to test function when also connected to the Select monitor as well as being used to perform computer reflashes. The black connector also has a ground lead and is used to obtain codes for the other system not accessible with the Select monitor on some vehicles such as the ABS or cruise.

      Do you mean the Spare fuses for the Under dash fuse block?

  42. I just read hundreds of your comments, T.Y. so much for this site! I have A problem now with my “daily Driver” which led me to your site. I have a 2001 Outback VDC H3. I got it one year ago, and it has run great all this time with no CEL at all. Last two weeks it started acting up. Once a week, the CEL would come on, cruise lite on, and re-set OFF after 3 drive cycles. Now it comes on every day…. accompanied with the VDC light while shaking and nearly stalling. Then it goes back to normal all day, CEL still on, VDC lite off. I am going to but a code reader tomorrow and post back to you. My fuel cap is always tight. I does not use oil: (dipstick went down only 1/4″ in 5000 miles). I replaced the fuel filter with OEM a week ago, but no fix. I did an OEM oil and oil filter 6 months ago. I hope it is just plug wires, but will scan it first.

  43. Hi Justin,

    I have a 02 ll bean outback with 106K on it and last month my check engine light was on, I took it to the dealer who said the error code is the infamous P0420, they clear the check engine light and it never come out again. Right now I kinda wanna get it fixed though it’s still off. I heard that if the light never comes out there’s a good chance that the rear O2 sensor needs to be replaced, but I don’t know if that’s really the case.

    Several days efore the P0420 came on, an error code of P0431 came on and they changed the front O2 sensor, then 0420 came on and after they cleared the check engine light the car still runs well, the MPG is normal and some times it does shake a little bit when the speed is over 75 mph. I always fuel my car with premium gas and change the oil every 3k miles.

    If you need any information just tell me, and thank you in advance for any information you’ll give.

    Thanks very much for your help!

    1. Hello Yue,

      Not sure what I can tell you?

      Did the Dealer diagnose the cause of the P0420 or just clear it?

      Repairing that code on the H6 cars can be expensive (not that the 4 cylinder is cheap) as such many ignore the P0420 code on that era Subaru, id obtain an estimate based on a thorough diagnoses and decide from there.


      1. Hi Justin,

        Thank you for your reply, the dealer just cleared the CEL light and told me, like what you said, it can cost a lot of money to fix it by replace both 3-way catalysts, but they didn’t do any detailed inspection. And what I heard is that if the CEL light, after being cleared, doesn’t come back again then it’s probably just a O2 sensor problem in which case you don’t need to change the 3-way catalysts, so I kinda wanna know is this true? Or it still could cost me a fortune?

        Many thanks!

  44. Justin

    2003 Forester XT 150K CEL had the code pulled by autozone P0428 didnt see a subaru code not sure if its a P0328 knock sensor code. thanks for any incite that you could provide.

  45. One additional piece of information, I just ran a short errand tonight and noticed that the Cruise Control button is flashing. I never use the Cruise Control. The button did not respond to pushing to try to turn it off. Anyway, maybe that is part of the issue and it will be something simple to fix.

    Thank you for your help,

  46. I have a 2004 Outback Legacy. I purchased it new. Over the years the “Check Engine” light has come on twice and I have taken it to the dealer who has then replaced the catalytic converter twice. It has been less than a year since the last time. Tonight the light came on again. I also had “everything” done to the car about three months ago; tune up, etc. It has 135k on it. What’s going on? I will call the dealer in the morning but why would the light come on now? If it is the converter again, is there some design flaw that would make it be a frequent repair? I’m in Northern California. Thank you for any information you can give.

    1. Hello Mary,

      You sound frustrated. The first thing you need to understand is there are hundreds of possible codes and only one light, just because the last two times it was a a P0420 Catalytic Convertor below Threshold does not mean that this time its not a something else.

      Knowing the code number each and every time is crucial, or you will be in the dark and frustrated.

      Without knowing the code there is no way I can begin to speculate on all of the possibilities, but if it does have another converter code, maybe you could consider not going to the Subaru Stealer anymore if its not a covered warranty type situation, they are really not qualified to accurately diagnose a repeated failure of a component, only swap out the old one for new.

      There are numerous Independent Shops that will go above and beyond for you, I would also like to point out that as the car ages it will be more common for the light to come on, a good solution is to own a code scanner for your self, they are no more difficult to own than a smart phone and can really go a long way in determining if the car is okay to drive.


      1. Thank you for your prompt reply. Yeah, I guess I am a bit frustrated. I just put about $3k of work into the car so that it would be “trouble free”. It is getting older but we love the car, especially my dog – he claims the cargo area. I know at some point I will have to trade it in for another Subaru. I was laid off recently so I don’t have a lot of money to spend on this latest problem.

        I do have an independent, very honest, mechanic near the house. He does work on Subaru but he is mostly a German car guy. He has done wonders on our older BMW. I will take it to him & see what the problem is. Thank you so much. Happy Holidays.

      2. Hi Justin,

        Just received a call from my independent mechanic and it is the catalytic converter (for the THIRD time). I would really like to know why this continues to happen. The last time I did question the dealer and he said that the grade of gas I use, etc. is fine. Is anyone else having converter problems?

        Thank you

        1. Hello Mary,

          I would say any of the below

          1. The reflash has not been done
          2. The Sensors are not being replaced
          3. There is a lean misfire thats gone unresolved
          4. The vehicle is used in a way thats causing premature failure.

          Know that its not common to need three convertors in three years, and no I wouldn’t replace it this time until a reason for failure has been found.


  47. This is a great forum. Interested to hear thoughts on this one.

    I have a 2001 Subaru Outback LLBean Edition. In January my Check Engine light came on. I took it to get it checked out and I was getting a code that said my Cat Converter was failing. I decided to get it fixed. Everything was working fine and then in April/May time frame the Check Engine lights comes back on. I take it in and the repair shop tells me to get the O2 sensors replaced. Everything working fine for about 2 weeks and then the Check Engine light comes back and saying that the Cat Converter has failed.

    I’m at a lost for what to do. Is it a misdiagnosis of the problem? Is the Cat defective? Anybody else have a similar problem? Interested to hear feedback.


    1. Hello Gregg,

      In my state we offer a warranty on all repairs we make, are repairs made in your state not required to have warranties?

      Also if aftermarket parts have been used it would fit that the replacement Catalyst failed already, which is why we only use the OE replacements here.

      I would talk with the shop and get some help


      1. Hey Justin,

        Thanks for the reply. I have since gotten the Bank 1 catalytic replaced via Warranty(got this done on 11/8) because the reader was telling the shop and me that it was a Bank 1 failure. Everything was fine until Sunday and then the Bank 1 failure re-appeared. They are now looking to see if it’s possible that one of the O2 sensors is now failing. I’m thinking it might need spark plugs. Any insights you might have would be great. Specifically interested if you’ve had situations where the cat was replaced, O2s replaced, and still seeing failures and if so, what ended up being the problem. To that end, what could be some of the alternative issues that’s causing the CEL to come on and give the failure codes.

          1. No, it’s an Aftermarket part. I know that is a potential issue but I can’t believe that would go bad in less than 2 days. Interestingly enough last night and today the CEL went off.

            Is there any logic to the fact that replacing the spark plugs could fix the issue?

            What does updating the sw entail? What is the fuel trim and how can this be fixed? I use mid-grade fuel, should I use low grade?

            Thanks Justin, really appreciate the feedback.

          2. That explains it, its not that it went bad, it was never good to begin with.

            The aftermarket convertors do not have enough precious metal in them to be a catalyst which is why they cost less, we have only ever found one that has shown any promise but even then the jury is still out.

            Platinum, Rhodium and Palladium are all very expensive, most aftermarket convertors use trace amounts of those metals.

            I would venture to guess the convertor is never reaching the “light off” point. If its not start with returning the convertor for an OE from Subaru I know it costs more but whats one that doesnt work worth?

  48. I have an 03 outback that I bought about a month ago, it’s been driving fine and still does, a couple of times in the last week as I reversed out of a park space it felt like something tried to engage, then 2 days ago the VDC and Engine light came on together. I hooked up a scan tool to the OBD connector which gave me 7 transmission codes and when I cleared them they came straight back when I started the vehicle.
    I also noticed that the stored memory plug was connected, I don’t know how long this has been the case as I just bought the car.
    When I plug the green connectors together the the engine light just flashes quickly and continuously without a break so it’s not giving me any codes through the test connector. The fans cut in and out with the plug connected, which they should do as I understand.

    I don’t think the transmission codes are accurate and it shifts well, some codes don’t even seem related to the transmission
    – 2 Stage twin Turbo System (doesn’t have turbo)
    – Differential pressure sensor
    – Tumble Generated valve position sensor 2 circuit low
    – Reverse inhibit control circuit
    – Brake switch circuit high
    – Brake switch circuit low
    – ATF temp sensor circuit high

    I have also cleaned all the earth points I can find and checked all the wiring connectors for corrosion too. With both the VDC and engine light on together I’m wondering if there is a common component like a speed sensor or something like that?
    Any ideas where I can go from here?

    1. I would have to say your Subaru has either the TCM in it, or your scanner is not capable of reading the codes properly.

      I would try another scan tool device, I have only ever used the Factory Subaru Scan tool when trying to read data from a Trans control Module, I actually wasn’t really aware there were other options for trans and ABS live data, I actually am not convinced there is by your post so far.

  49. AAAH Just bought a car, 30 miles in check engine light comes on. Checked it at Auto Parts and its P0028. Thought it was the oil or gas cap so I checked the oil at Jiffy lube, they say its completely full and the oil is clean. They turned off the check engine light for me thinking it could’ve been a “misread”. I keep driving – 100 miles in check engine light is on AGAIN and cruise control flashes. I drove 350 miles (in one day) and rechecked the code at a mechanic for $180.
    Mechanics report:

    Scanned vehicle for codes and retrieved
    p0028 – left oil switching valve solenoid malfunction
    p0026 – Right oil switching valve

    Accessed harness for both left and right bank VVL oil pressure switch and circuits both OK at this time. Proper power and ground present for both solenoids, both show switching when needed or activated. Checked oil and found to be clean, possible condition codes were set due to lack of oil pressure, and/or oil itself. System works normal at this time. Possible oil passaged slugged up causing intermittent issues, which would require further disassembly.

    I’ve driven the car for 450 miles so far and nothing drastic has happened, I can hit high speeds no problem. There has been times where if i press on the gas hard to accelerate and the RMPs shoot up but the car gains speed slowly, Im afraid so I just don’t do that anymore.

    It also smells like plastic is burning! Its from the engine, and the smell doesn’t go away for a while, it lingers for 30-60mins after car is turned off. I constantly check for leaks but there is no oil drips. The engine doesn’t sound bad, no clicking clunking ect. and i can’t really tell if its idling rough, it seems smooth to me. The car doesn’t over heat, but it is low on coolant. Towards the end of the long drive the breaks started squeaking a little.

    After my online research it could be:
    -Intake valve Solenoid are loose
    -Sludge build up in car
    -Oil burning or oil leak
    -Plastic bag melted on exhaust
    -Knock sensor…?

    What’s your opinion on this?? What would you do next and what should i keep my eye on?

    1. Hello Andy,

      I would start with a oil change with good oil and a Great Filter, from there if the problem persists most likely it needs a solenoid or two.

      9 times out of ten we find that it has a cheap oil filter causing all of the issues.

      We have corrected these codes on many Subaru vehicles with just an oil change. But we have also found scored cylinder heads from repeatedly stretching out the oil changes to far ultimately be the culprit as well, I just based on the info you can’t give me know the exact cause from here, but what the ECM is seeing is insufficient Cam shaft timing advance under load when it sets those codes.

      Hope that helps


  50. Hi Justin,

    I drive a 2001 Subaru Outback, and my check engine light and VCD light came on after work today on my drive home. The VCD went off after a couple minutes, but check engine stayed on. I live in Phoenix and it is about 110 degrees today. I made sure the gas tank was full and the cap is on tight. At one point while I was waiting at a stoplight, my car did something that almost seemed as if it was going to stall, but it was fine. I took it to an auto parts store to see if they could read the code, but they said my computer wasn’t communicating with their reader. The guy at the shop said it sounds like a “drivability” issue. When I turned my car back on, the light was off. I am still worried there is something wrong with it, but do you have any idea what it might be? Thanks so much for your information.

    1. HI Lily,

      I wish I could help, but without the code there is just now way of knowing really where to start.

      Some basic code readers cant properly scan for codes on certain models, or someone inexperienced was trying to use the tool.

      Common issues to the 2001 would be the TPS or (throttle position sensor) as well as the harness for a Stall.

      I would seek out a Subaru shop near you and be ready to take it them at the next occurrence.

      Hope that helps


  51. Good day Justin,
    I’ve read most of the posts on the CEL, but haven’t seen what I’m experiencing.
    About a month ago, while driving in the rain, the throttle went into idle, and would not respond.CEL on, steady, cruise fleshing.
    Got the car towed, and the next day, (nice and sunny), the car ran perfect. I disconnected the batt., the light went out.
    Today, I drove out of the house after a day’s worth of rain yesterday, drove for about 10 minutes, and the same thing happened. I drove back to the house at 20KM/hr, let the car get nice and hot, and I connected my new OBD11 scanner; it showed 1 code, but I hit the wrong buttons, and reset the light. The car ran fine all day.

    I would like to know what can cause the throttle to not respond, and stay at idle. It appears the I have water getting in a connector for a time; I was thinking the TPS, but that’s just a guess.
    I realise I have no code, but can you give me a possible cause, for next time…
    2006 outback, 3.0, auto. ,182,000 KMS.

    Best regards,

    1. Hello Herman,

      It would be better to stop clearing and disconnecting the battery, instead try to gain some data so yu can get to the bottom of it.

      It could be an issue with the drive by wire system, this includes a connection issue. The key is going to be to get the code the next time and move from there.

      Nothing typical stands out to me at this time. Sorry..


  52. Justin,

    Going over this site, I always see a lot of good information. I’m pretty sure of the path to follow, but, maybe need assurances. Car is a 2000 OBW w/138k.
    This is my scenario:
    CEL came on 6/28/13 while on a trip. Notice slight rough idling. Came home CEL was off. 2 weeks later on another trip CEL came on again, notice more rough idling/stuttering. Came home and connected a tester – misfire cyl 2. I swapped out both plugs 2 & 4 on 7/16/13. Old plugs looked okay. Had to make another trip on 7/27/13. I brought extra plugs, tools, Code reader (all in case). On the way over, noticeable rough idling, CEL back on and about 15 miles from dest, CEL flashed for about 5 secs. On my way out that day (about an hour 1/2 later) idling was so bad I pulled over swapped number 2 again (reader specified #2 misfire) and came home. Now I’m looking at the ignition coil or o2 sensor as the issue. Am I looking correctly? Please advise. The car goes in the shop on 8/1/13 for sway bar links, so, I could have them take a look. I’d rather do a DIY fix if possible. Any advice would be appreciated.
    Also, it was your guidance that assisted me in ID’ing my head gasket prob, thanks for that one!


  53. Hi, I have a 2004 Limited Edition Legacy wagon. After I added windshield fluid and filled up with non-ethanol gas the Check Engine light came on. Checked gas cap was fine. Took it off and checked for debris and put it back on. Light still on. Cleaned battery due to abundance of leakage with baking soda and water. Found a crack at base of Neg. Post. Replaced battery/cleaned up mess. Turned car on CEngine light still on. Turned car off and turned back on the light went out, But only for a short while. I will go add more gas and make sure cap is tight and see if that makes a diff. I am sure it won’t. Online said it could be Catalyst sysem or fault codes run amok. Did not know if I should ck fuses. Does need an oil change. and running a tad bit warmer than normal. Guess I need to call Subaru. Let me know what u think so I am better informed when I go into the dealer. Thank you

  54. Wow! Love the website. You are a bundle of info. I went through all postings available and was able to find a code like mine, P0457. You had stated to the writer that it could be a gas cap or a solenoid. I had it checked about a month ago when light first came on. First establishment stated the code dealt with emissions but found no leak, thought maybe I did not tighten gas gap properly and they reset it. It came on again about 2 weeks later, day before it had to be inspected…of coarse! This time my usual auto establishment checked it, they said with a $25,000 dollar machine and did not find any leaks but failed car and reset light. I had to drive it for 200-300 miles and bring it back to see if light came back on. It didn’t, they inspected car again, it passed and all was well….until last week. Driving normally on highway and bling…light on again. It doesn’t have any obvious changes in performance but there must be something. On the car inspection report, the gas cap passed. I drive a 2003 Forester. I know it needs to be looked at but I seriously have low $. What is a solenoid? Does that have to do with emissions? I don’t want to be an auto shop guessing game because I am a girl and haven’t a clue about cars. Can you maybe list what most of the problems could be so when I can get it looked at, I can make sure they are looking in the right direction? Any guidance is appreciated. I know you cant properly diagnose without physically checking and from older postings, I know I need to have it checked. Thank you in advance for your help! 🙂

    1. Hello Dena,

      A solenoid is a electrical device commanded on by the computer to open and close, when it opens and closes fuel vapor is diverted or omitted. Your car has many solenoids, in the case of P0457 we have observed some with small pin hole leaks at the Fuel fill tube from rotting (mostly with east coast cars) as well as small pin hole leaks and defective solenoids. If where you take the car cant get to the bottom of it, You either wait until its more prevalent or have a good shop try what seems the most logical.


  55. I have a Subaru Forester that displays a flashing check engine light and it vibrates when idle. I took it to a mechanic who claimed that it was misfiring on cylinders 1 and 3 and needed new spark plugs.

    After the vehicle was taken into the bay, other mechanics allegedly performed the repairs. After they gave me the keys, the check engine light was off but the SUV still had the violent shake. I asked the mechanic at the service desk why it still vibrated. He didn’t even look at the vehicle and shrugged saying that he didn’t know, but that the check engine light was off (he didn’t even come outside to confirm this for himself).
    The next day I was driving the SUV on a rural road (speed limit 55 mph) gradually decreasing speed by increments of 5 mph until reaching 30 mph city speed limit. As I sat at a traffic light, the Forester continued shaking. Then the check engine light flashed three times then went off.
    My concern is this: since 2012 I’ve taken the Forester to several different mechanics for this problem. The Forester would be slow to accelerate from a stop position. Then one day it wouldn’t start. When I attempted to start it, the vehicle shook violently so I took it to a mechanic who claimed that I needed a new water pump.
    I paid the 680 dollars for the replacement and went back a few days later to pick up my vehicle. The vehicle started up but shook violently, the mechanic said that I had a problem with misfire and needed new cylinder and spark plugs but did not even recommend the work be done at his repair shop. I felt shafted on the original diagnostic and took it to a second shop who also claimeed that it needed a tune up which included spark plugs at a cost of over $700.
    After I paid the fee I waited for the repairs which they claimed would be completed by the end of the day 9I took it in at 8 AM). By the end of the day I had not heard from them and called to ask about the progress of repairs. They told me that the job was taking longer than expected and tthat they would call me back at 10 AM the next day (a Saturday).
    By 11:30 AM that Saturday morning I hadn’t received a call from them and decided to call the mechanics to find out what was going on. I was again told the repairs were taking longer than expected and that the Forester would be ready by Monday morning (just before Independence Day).
    On Monday morning I decided not to wait for their call and to get my vehicle back. When I got there the mechanic rushed out to tell me that my tune up didn’t work and that they wanted an additional 900 to take the engine apart for a detailed microscopic diagnosis. I refused, so they backed the SUV out of the bay and a lot of blue smoke billowed from the rear exhaust. I asked why and they claimed that smoke was from the diagnosis.
    I turned them in for false advertising but nothing was doen about it, but interestingly that shop did close down some months later.
    So fast forward to this late srping of this year. I took it into a third repair shop who said we had problems with the cylinder and spark plugs. I paid a smaller fee for the repairs ( had believed them because I had already suspected the mechanics at the second shop had not done any repairs whatsoever). The next day they told me that my vehicle was ready and that aside from a slight vibration the vehicle drove allright. When I went to get it, they told me that because my vehicle hadn’t been driven in nearly a year, they suggested I put some engine cleaning fluid in to clear out the old gas, they said if I had problems with the SUV to bring it back in.
    After driving around for an hour, I stopped and purchased the fuel cleaner and added it to the gas tank and filled up on a full tank of gas (as they recommended). But as soon as I turned the vehicle back on, the light came back on. I took it back in and they did more work on it and when I picked it up the vehicle still had the vibration but not light.
    I took it for a drive on the rural route (the same one that I did yesterday) and the check engine light came on but then something new happened: it began to flash three times then held steady.
    They looked at it again and then said they fixed the problem but it came right back. So I took it to this most recent repair shop (fourth one since this problem began).
    Why is it that four mechanic shops say the same thing (and I pay three of them for the same problem) but it doesn’t get fixed? To me it seems like a scam. Are there ANY honest mechanics who will fix this problem?

    1. Hello Joesph,

      The key to obtaining good service with any service provider is to have a long standing trusting relationship. Like going to the same barber cause they know how you like your hair cut, or the same dentist or Doctor as they have all of your records.

      Anytime you bounce form one shop to another this will inevitably be the result.

      The car can not be driven with a flashing check engine light, and you must find a good place to take it and stick with them until its resolved.

      Have you tried taking the car back to any of these shops?


  56. Hello Again,

    This may be of some help as to the behavior of my 2001 Subaru Outback prior to the “LIQUID PATCH”! and code that read a very small leak in the cooling system (I think it was stated that way.)

    My car ticked prior and it was noticeable. It does not now.

    It overheated two weeks after the check engine light went on back in Oct., 2012. (And I mean, literally two weeks later, not two solid weeks of driving. I stopped driving my car and did so only to get to doctor, fuel up, and grocery shop.) We stopped the car immediately. No smoke, nothing. Ten minutes later, in the middle of the road, smoke or steam rather came out and a tiny dot or gush of coolant spouted out – as if the coolant was GONE. The moment that light light originally came on we noticed a stain on the ground under the car. We hadn’t found out anything at that time and by the time the patch was done there were probably twenty stains – Large but not wet – as with a slow leak. In hindsight, the stains were not consistent. They did not appear daily but we did witness two after heavy driving on doctor appointed days. That overheat wa probably due to coolant being non-existant.

    The serviceman asked me three or four times if I was going to be driving my car??? Uh, that the idea. He told me to drive it for two weeks – kept saying two weeks, then to bring it back and they’ll take care of the other things I needed – oil change, etc. He refused an oil change until I come back. Was that for refund reasons possibly (again, I’m worried) to let time pass or to truely see if the patch worked. Problem again, if it does hold, I have no refund fight after waiting that period. I can fight if this is all b.s. because IT WAS INTENDED TO BE LOOKED AT FIRST, NOT REPAIRED. I’m not sure about waiting two weeks.

    I’m going to have codes run tomorrow at Nappa. I’d like to know myself if the only code that remains is indeed the latter – a gas cap issue (or worse).

    The car shimmies when we start it and THAT started a couple of months ago. That shake and shimmy I’ve seen in older cars when they’re first fired up. It never ever did that. It started on a dime.

    A deer darted out in the middle of the road last year and there was no time. In a flash we hit it and it was sucked right under the car. The deer itself was quite gruesome. A rattle bagan. The young man, that friend I spoke of at the very start of my first post said he took care of that later finding that he had torn off the heat shield in order to resolve the issue. (You really wouldn’t believe the trouble we’ve had with mechanics nor where we live. You’d never in your life expect the kind of service we’ve experienced considering what we pay to live in a “safe” and beautiful area. We were told we could do without a heat shield. I’m not so worried about that because we have the means to have that repaid or replaced by that mechanic. We can’t have problems with every mechanic, either. There’s got to be someone who truely knows how to repair our vehicle OR SAY THEY CAN’T so we can move on! Being honest here in saying first I have no understanding of this: could any damage under that car have triggered that engine light? It was put on racks and there was some slight pitting (as with hail damage to a cars’ hoods but less in severity) and loose shields but no noticeable cracks or large dents/dings. There is rust so…..

    I’m SURE you’re exhausted by now but I’d really appreciate some feedback. I just need something solid to go by. Was that liquid patch a joke? We can’t be stranded. My husband is 65 and still weak. I can’t have him out in the middle of the road waiting on a tow. If it was excessively hot or cold he’d have no way of releaving the discomfort inside the car.

    What do you think and what should I do next?

    Thank You So Very Much,
    Tina & Lou

  57. Hello,

    I’m in desperate need of help with this situation. I have a 2001 Subaru Outback H4. My check engine light came on some months back – October (2012) to be exact.

    First I’d like to say that I’m neurotic about the care of my vehicle and am a responsible person in general. I’m a Caregiver to a Cancer survivor who had just come home from hospital that very October as did Hurricane Sandy and we live right on the Long Island Sound. I suppose we were due for a disaster or two. Anyway, my main concern is that Cancer survivor as he is my husband. Our vehicle is EVERYTHING to us. We cannot sell it at this point.

    The “transportation”: This thing – as it’s now become – needs to keep on ticking and it truely is a remarkable vehicle. The engine light: We found out, after a friend of my husband lied to us about how little he really knew about cars screwed us royally, that there was a tiny leak in the #4 cylinder. We cannot get an honest answer out of anyone. We were/are very cautious.

    We were recommended by several people to a service station in a neighboring town. We dropped our car off for an inspection for what we were told on four occasions by the owner that there is a seal that can repair this problem. I’ve heard of this but know nothing other than some are fans and some are not – and for various reasons. I was told to leave the vehicle for 3 hours as it would take them some time to look into whether or not my car was a candidate and if this “seal” would fit. The word he used TWICE was “FIT”. I pictured an actual tangible “part”. I called to check on the Outback and was told that they were just getting to it and would call me back to let me know when to pick it up. I asked “Are you going to let me know before I head out what the issue is or when I come to pick it up?” (We were eager to finally find out what the problem was and what we could do about it.) The serviceman studdered slightly and said (rushed) “Uh, yeah, yeah, we gonna tell you when you come.”

    I get a call and the same man tells me the car is all ready. I didn’t mind the 3 hours dropped off in the early morning turned into a 5 o’clock pick-up bacause we had news. So I said “Great! So what is it? What did you find?” The serviceman says “Oh, no. The car is all ready. We finish the repair and it’s all ready to pickup.” I wash shocked! I couldn’t believe they had turned an insoection of a car into a repair without a phone call AT ALL! I knew from the onset from the owner himself that if my car was indeed a candidate for this repair “patch”, “seal”, that it would be a $400.00 job. I was prepared for war and started asking questions. So the serviceman goes on to tell me that there are no further problems “It’s all fix. All fix!” and that they were going to give us a break in price and only charge us $299.00 + tax hoping to get us as a customer exactly stated. I turned that shock and war-mode into complete joy.

    Problem: Very next day light comes back on. We were shown a code that was not – supposedly – regarding possibly a fuel cap (or worse I’m now dreading). The problem with that code is that it originaly popped up the very moment that the gasket lead code showed up. I do understand quite a bit and I urge other women to learn but I’m not knowledgeable about this. If they really do believe in this “seal”, “patch” (and maybe you, too) and that it has worked and that (owner) “I’ve done it with MANY vehicle and I’ve never had a problem and they’ve lasted for years.” then I have questions:

    1. Why did the first serviceman I walked up to when I went back to have that light looked at look at what I was holding in my hands (a note with questions to ask them) and look at my purse, nervously, turn around and walk off turning into a running-walk looking back laughing when I tried to ask him if he knew what kind of part was used on my vehicle?

    2. Why did that same man refuse to talk to me when I again approached him as he was waiting in my vehicle that needed to be moved? I had to open the door myself! I knocked on the window and he rolled his eyes to the side looking at me and froze!

    3. Is it to be expected that the vehicles’ owner would want a simple question asnwered by the owner of the shop as to what kind of part – SPRAY??? – was used on my vehicle????? I made darn sure to be as polite, nice and welcoming as to get a darn answer. The owner, TOO, started looking at my HANDS??? (Did this guy think I was recording him???), my purse and said in a whisper (unreal!) “liquid”. I asked if he believed in this product and if he really thought it would work and all I got was nod with a dead-straight face.

    I’m worried! There was a high school friend of my husbands’ there, too. He is friends with that owner and a retired police officer. Everything looks good on paper. The place is medium in size with three double bays, 6 gas pumps, orderly, with jam packed customers and at least 4 serviceman employed in addition to the owner. Is this “secret liguid” a true patch? Can it last for two years or more if we keep everything in ship-shape? Should I go to the bank and inform them of this and the fact that I had no idea my car was being repaired with something I’m not allowed to know about and fight the transaction? Am I over-reacting? My husband and I need some help here. I’d appreciate ANY ADVICE &/OR FEEDBACK FROM ANYONE at this point. I’m worried about getting my husband of 15 years to his oncologists’ and other speacialists’ appointments and I want to know if we’ve just been had.

    Thank You for Your Time,
    Tina & Lou

    1. Hello Tinamarie

      Love to help but I just don’t understand your post or questions.

      There is no way on earth I can answer a question about an event that took place at another place of business. There is also no way I can know what the intent of the other place of business was, or if they thought they were trying to help you? Next what were the original Symptoms that they were trying to fix, you moved into a long post about the conduct of the shop and your personal situation which both are very important for you but don’t help me try and help you with your car.

      There is no magic in a bottle either by the way, there is a belief by some that a stop leak may resolve leaks, all it does is put off the inevitable at the expense of other components.


  58. Hello, I owe a 2006 subaru legacu and just recently the check engine light came on. Due to the cel coming on my cruise control light started blinking. I had did some research of my own and they had said that the cruise control light blinks the moment my cel comes on because it disables my cruise control but my car is running great. I am planning on going to autozone and getting a diagnostic, I just wanted to know what the most common reasons the cel would come on and what little tips and tricks i can use to solve this on my own

    1. Hello Ashlie,

      1. Auto zone does not diagnose, they scan for codes. Sometimes they will give you good advice based on component codes, but have no capacity to diagnose a conditional code.
      2. You can buy your own code scanner for under $75.00 and keep it in the car somewhere and will at least be cable to scan for codes yourself.

      Some issues are straight forward and easy, others are not, there is no specific advise I can offer without the code, then some data.


  59. Hi Justin
    Thanks for making this information available.
    I have a MY04 Forester XS in Australia. The CEL is on and I had my mechanic diagnose it with code P0032, the front air fuel o2 sensor. I had a brand new one fitted (Denso), had the code cleared but the CEL is still on after 2 weeks (250 kms of driving). It’s on constant.
    I have also now connected the green wires to reset the ECU (I can’t see any black wires). The reset seemed to be successful – when I started the car the CEL pulsated about every second. I believe this is normal. I drove for a bit then stopped, switched off the ignition and disconnected the green wires.
    When I started the car again, the CEL is back on constantly.
    Have you any advice? I’m lost.


    1. Hi Sean,

      You have not indicated if its the same code prior to replacing the 02 sensor?

      If it was than the Diagnoses may have been incomplete or the sensor defective.

      If its a different code its a different issue.


      1. Hi Justin
        It’s the same P0032 code.
        I really can’t believe this but tonight I decided to pull the bonnet and have a look at the sensor myself (2 weeks after being fitted by the mechanic). To my horror I discovered that the harness wasn’t connected properly.
        I clicked it together, did the green wire ECU reset, started the car a few times and the CEL has cleared. Took it for a 30 min run and it has stayed off. It amazes me how a qualified mechanic didn’t click it in place – there doesn’t appear to me be much room for error.

        Anyway, I’m relieved it appears to be fixed. But I’d like to know if I need to take any further action given that I’ve essentially been driving the car for 2 weeks without any air/fuel sensor? Will the car reprogram itself automatically to run at optimum levels, including idling etc, given I’ve also reset the ECU?

        1. Hi Sean,

          That’s awful. The ECM will go into a fixed or “pre programmed” mode when ever it fails to obtain data from a sensor this is always going to allow the car to run rich as a lean misfire can cause damage, your fuel economy was probably awful and it wouldn’t have run its best.

          A spirited drive will help blow out any carbon from excessive fuel, and I would change the oil, its probably diluted.

          Hope that helps


  60. Hi Justin,
    I really appreciate your blog and your extremely helpful postings.

    I have a 2002 Subaru WRX turbo wagon- 105,000 miles, original owner.
    Last month the check engine light came on, and a some dark smoke was visible through the hood. My local (10 years)
    mechanic gave me an estimate of $1,350 to fix the problems
    outlined by the CEL codes:
    Replace air intake boot,
    Replace power steering hose assembly,
    Reseal oil pan,
    Replace 2 drive belts,
    Lube, Oil and filter change

    I drove the car to Smog check and the engine light came back on during the test. Failed the test. When I came back to the shop, he quoted me a list an additional $1,300 of work, including listed parts that were double the price of KBB parts listings online.

    This time I went to the Subaru dealer, where I originally bought the car. They told me the air intake boot assembly had not been replaced, and an additional $1,400 of work was needed to pass smog and be able to drive my commute safely:

    Replace Turbo intake Boot,
    Replace 02 sensor,
    Gasket intake Manifold,
    Air Fuel Ratio Sensor,
    Repair 2 o-rings
    Cooling system and fluid refill.

    They loaned me a rented car and called me the next day with a passed smog check test. As I’m driving home after the smog test, the check engine light came back on. Car drives great and feels good.

    I have spent $2,800 on repairs this month. I realize after reading your column and speaking to the Subaru tech, that CEL codes could involve any number of different things going wrong. I have run out of money this month.
    Where do I go from here? Can I drive this car safely or is it time to trade this car in for a new one?
    Thanks for your time and expertise,

    1. Hi Ric,

      The first thing you need to understand is you need to know what code was set at each occurrence. Next without you telling me what code is set I cant tell you if you could have a loose gas cap or a failing Convertor.

      No reason to give up on a car with 105k, but you do need to find the right person to service it, s this one thing will change your entire ownership experience.


  61. hi justin.
    i own a subaru legacy ts-r in new zealand and my check engine light comes on when i start driving car but it turns off when car turns off. any suggestions. i took it to a mechanic and he said it was a a cam sensor. so he fixed it but the check engine light still comes on after driving for some time. any suggestions will be much appreciated thanks.

    1. I may not be able to help much as the Model Subaru you have in New Zealand is going to be different than what I am used to here. Having said all of that if you wanted to fly me in, Id get to the bottom of it, and Id love to see where the lord of the rings movies were filmed.

      On a serious note

      With out a code there is nothing I can tell you, even if you give me a code. I could still be at a disadvantage due to the model thing.

      Subaru had an updated cam and crank sensor kit for the 1995 to 1999 Subaru’s here in the states. Because I believe the TSR to be a 2.0l DOHC NA( Which I have never seen) I don’t think there is anything exotic such as Variable Valve train solenoids, I would be concerned the timing belt may be stretched if a cam sensor did not resolve a cam sensor code .

      Thats all I can offer

      Hope it helps


  62. Hi Justin,

    My service engine light is on and the cruise control is flashing/doesn’t work. Engine was sputtering a couple of days ago when these issues arose, although hasn’t sputtered since that time. Dealer says I have an engine misfire on 1 and 3 cylinders. They said the coil pack should be replaced in order to fix the problem. Also say I need a new air filter. Quoted $320. Does this seem accurate and reasonable? Is this repair something I could easily do myself? Should we try anything else first? Also, I’m going on a 700 mile road trip soon. Your advice would be much appreciated.

    1. Cant comment on the accuracy as I have not inspected it. A failed coil will cause a misfire however.

      I have no idea what your capabilities are or the content of your tool box to know if you can do it, it requires basic metric hand tools.

      You cant drive it with a misfire you ruin the Catalyst and maybe the engine.


  63. My 2003 Impreza TS 2.5L with only, unbelievable but true, 25,000 miles on it has a CEL code of P0032, Heater Control Circuit High Bank 1 Sensor 1, which is something to do with the Air/Fuel Ratio Sensor heater either being open circuit or no voltage getting to it. I would like to determine what the problem is without jacking up the car as I don’t have a heated garage and a jack and jack stands or ramps to use where I live where it is now Winter and cold. I need some information such as what fuse and relay are involved in powering the sensor’s heater element so that I can test the circuit through the wiring harness from those points. Would someone please post it here. Thanks.

      1. I got the 2002 Subaru Impreza Service Manual ,which also applies to the 2003 model, and traced the circuits. The A/F ratio sensor is wired through the wiring harness directly to the ECU without any fuse protecting the ECM from a short-circuit in the wiring harness or elsewhere. I hope it’s not a short-circuit in the wiring harness because that can damage the ECU.

  64. Before I say anything, I have been reading forums, and I don’t have obd codes yet, as the problem started just before reading said forums.
    1999 Forester, seems to be idling rough (does good job of shaking car), checked fluid levels, all at full levels. She can’t drive the car on the interstate without warming it up for like 20 minutes (different problem I think, car sat in Haiti undriven for a year, we think some of seals/gaskets may have dried up). I don’t know much about under the hood, any suggestions?

    Thanks for your help,

    (ps love the site, thanks for doing this on your free time)

    1. Have a code scan performed and take things from there..

      Sorry, I just cant say this enough apparently, but the light means check the Engine Control Module for codes, and nothing else but that there is a codes stored and that code should be evaluated for the need of repair.


  65. I have an ’06 OBXT with just under 90K miles. About two weeks ago while driving on the freeway I was giving it some gas and it seemed like someone had pulled the engine out for a second and the CEL came on with flashing cruise light. I took it in to my regular mechanic and he told me the code was for a waste gate sensor which he replaced and the problem happened again on the way home from picking it up. I took it back and he looked at it again and stated that there was a problem with a valve (he said it was more like a diaphragm) and it was holding sometimes and sometimes it wasn’t. Told me that that can’t be replaced but the entire turbo would need replaced. I went and picked it up.

    Drove it to work today and hammered it as much as possible to try and duplicate the condition. It seems to happen when the RPMs get to around 4000. Any suggestions? Should I take it back to my regular mechanic and get a new turbo, or should I take it to the dealership and let them have a crack at it?

    Thanks in advance!!!

    1. Hi Lindsay,

      Did he offer what the boost Values were?

      As far as where to take it, if your guy has confidence in his diagnoses it should be fine to have him go ahead I would think.

      We have replaced Turbos for that set of circumstances as well.

      Hope that helps


  66. hi i have a 1996 subaru sport uk model the check engine light comes on now and again and the car seems like its lost power but once the light goes out after about 5 minutes the car has all its power back. any ideas what could be causing this. could u also tell me if it has a diagnostic port and if so where is it located

    1. It has a Diagnostic port, in the US, its required by law to be on the left of the Steering column at the bottom of the dash.

      I do however know that there are UK, JDM spec cars that have diagnostic ports, and types different than what we see in the US.

      Sorry I cant offer you more.


  67. Hello Justin,
    I have a 2005 Subaru Legacy GT with the turbocharged 2.5L engine and automatic transmision. It has 102,500 miles on it. I bought it with 69,000 miles on it 3 years ago. A couple times i guess the gas cap was loose and the check engine light turned on and cruise control light started flashing. I replaced the gas cap and havent had a problem since. This past week the check engine light has been turning on, but the cruise light doesnt flash. The odd thng is that the autoxray code reader that i have doesnt read any codes and actually says that the MIL light is off even when it is on. The check engine light sometimes stays on for a few minutes then turns off. Sometimes it only lights for a few seconds or maybe for a split second then turns off. It has been doing this off and on thing for several days and doesnt set a code or a pending code. But the engine seems to run fine. The only thing I notice is that the idle is a little rough but its been like that for years. I dont know when the spark plug change interval is for this car. Could that be the issue? Some slight misfiring caused by worn plugs? The engine has no problem starting up.
    Could it be bad gas? Since i dont know when the plugs were last changed im going to try that first. In the next few months Ill need to change the timing bel as well.

    Thanks for any suggestions.

  68. Hello Justin,
    About 2 months ago my mechanic was performing regular maintenance & an all-systems-check on my 1995 Subaru Legacy Brighton Wagon (2.2L H4 engine) (186k mile vehicle) since I was moving/driving across country to Arizona. Long story short, they forgot to tighten the oil drain plug, which led to engine failure. They replaced my engine with a used 125k mile one and replaced a coolant sensor and oil sending unit on the “new” engine (was tripping the engine light). I had my transmission flushed at a DIFFERENT garage who said my clutch-pak was wearing out, so they inserted the fuse to disengage my AWD. All seemed well. I drove 2k miles (very weight-overloaded) with no problems. Now in Phoenix for 2 weeks, my car did not want to start today (nothing happened when turned ignition several times). After making a long beep when it did start, my engine light is back on but with codes P1101 & P0420. Also, after driving a bit and turning it off my car is pinging loudly and it kind of smells like a skunk. The kid at AutoZone told me the gas sucks here, which might be the reason for P0420, and that the heat kills sensors. I am going to add some good injector cleaner to the tank and get only Shell gas (saw the tip in an earlier post). I have all of my sensors from my original engine. Should I install my old O2 sensor or is that a bad idea? How long after I try injector cleaner, different gas, and a possible O2 sensor change should I wait to take it to a Suby dealer? What would be the reason for the P1101 code? Is it related to installing the AWD override fuse? (I’m a missionary and on a seriously tight budget.) Any FREE help is highly appreciated! Thanks Justin.

    1. Hello Aaron,

      The P0101 code is suggesting there may be an issue with the readings from the Mass air flow sensor to the Computer.

      Thats the component that needs to be evaluated first. In order to do so the Voltage readings need to be put up against whats a nominal reading at a given temperature and “engine speed” or RPM’s.

      I can understand the the funds situation, but what I have laid out above is what needs to happen, and if you don’t have a scan tool or a DVOM and the ability to use and understand them its tough to tell you how to proceed other then say you can throw an expensive part at it based on my guess from your post, or have it diagnosed somewhere. It will run poorly if it has a Mass air flow sensor sensor or range issue.


  69. Hello Justin,
    I have a 1995 Subaru Legacy Brighton Wagon (2.2L H4 engine). About 2 months ago my regular mechanic was performing regular maintenance & an all-systems-check on my 186k mile vehicle since I was moving/driving across country to Arizona. Long story short, they forgot to tighten the oil drain plug, which led to engine failure. They replaced my engine with a used 125k mile one and replaced a coolant sensor and oil sending unit on the “new” engine (was tripping the engine light). I had my transmission flushed at a DIFFERENT garage who said my clutch-pak was wearing out, so they inserted the fuse to disengage my AWD. All seemed well. I drove 2k miles (very weight-overloaded) with no problems. Now in Phoenix for 2 weeks, my car did not want to start today (nothing happened when turned ignition several times). After making a long beep when it did start, my engine light is back on but with codes P1101 & P0420. Also, after driving a bit and turning it off my car is pinging loudly and it kind of smells like a skunk. The kid at AutoZone told me the gas sucks here, which might be the reason for P0420, and that the heat kills sensors. I am going to add some good injector cleaner to the tank and get only Shell gas (saw the tip in an earlier post). I have all of my sensors from my original engine. Should I install my old O2 sensor or is that a bad idea? How long after I try injector cleaner, different gas, and a possible O2 sensor change should I wait to take it to a Suby dealer? What would be the reason for the P1101 code? Is it related to installing the AWD override fuse? (I’m a missionary and on a seriously tight budget.) Any FREE help is highly appreciated! Thanks Justin.

  70. On my 2004 Subaru Forester turbo, the check engine light (CEL) was flashing after a service and I discovered that someone had connected the green diagnostic plug. I have now disconnected it and the CEL is not flashing. Thank you Justin for great information, and Google for helping me find your site.
    I will take it back to the dealer that did the service as the No. 4 15A fuse has blown for the side mirrors and cigarette lighter. I replaced the blown fuse with the spare 15A and started the engine and it blew again.

  71. Justin,
    Neighbor has a 1994 Legacy that sprung a leak in the radiator. The shop he recently bought it from replaced the radiator and tested the vehicle. When my neighbor drove the car home from the shop, he noticed that the check engine light was on. He asked the shop what they thought and they advised him to go through a number of drive cycles before worrying much about it. Is it likely that the overheating that went along with the ruptured radiator tripped the cel? How do we find out how many drive cycles and of what duration they should be before expecting the light to reset or to stay on? Is there anywhere to read about the possible codes that could be involved? Thanks for the help. Your posts are very informative!

  72. hi i have a 1997 subaru liberty rx 2.5 liter awd
    the engine light comes up as soon as i get to a contant speed and stay on the same rmp for 20seconds or so.

    code 32 comes up.

    oxygen sensors.

    i have replaced the oxygen sensors twice.

    bosch and ngk

    replaced spark plugs with ngk plugs as listed.

    cleaned throttle body.

    carried out upper cylinder cleaner.

    air filter is new.

    i have tryed 3 different test air flow meters all didnt help

    i am a mechanic by trade

    any ideas or paths i should go down next?


    1. Hi Ben,

      You need to obtain the diagnostic flow chart for that code from the service manual and follow it, I am in the U.S., your model of Subaru doesn’t exist here.



  73. I just wanted to say THANK YOU!

    I just bought a wrecked 01 Impreza Outback and I’m turning it into a buggy. I’ve removed a lot of the systems from the original harness while waiting on parts to fix a crushed cam gear and timing belt.
    I finally started the car and the CEL was flashing. I assumed it was the deleted air bag system or something. I’ve spent 2 days trying to figure the problem out. I really wanted the diagnostics to work and didn’t want to reinstall all the stuff I don’t need.

    It turned out to be the green diagnostic plug was connected, which I’m positive I didn’t do. I can’t help but wonder how long the previous owner just ignored that flashing light.

    Anyway, thank you so much for this information. Years after you first posted it on here it is still helping people. This is the kind of compassion that would make me a loyal customer of yours if I didn’t live 3000 miles away. I hope your customers do appreciate what they have in your honesty and willingness to help others, not just make a buck.

    David Fox

  74. Hello! I just wanted to put in my 2 scents. I guess I should first of all say that my 2004 Subaru Legacy Wagon was a gift from my parents (not one I chose). I currently has 189,000 miles on it. However, for the last 3 years my check engine light has come on and off periodically. It seems that when I don’t drive it for awhile the light goes off but when I start driving it more – it comes on. I have had 2 (count them 2) catalytic converters put on, a new front and rear O2 sensor and yet…..still have the problem. I have also had my engine rebuilt because of a cracked head gasket. I understand that cars have problems esp. when they get old but the whole check engine light is a little bit annoying. I am sunk a lot of money into the car and still have the problem. The code that always reads is something like emissions is running below efficiency. Something like that….can you please tell me what the heck is wrong with this car?

    1. Hello Brittany,

      Here is what I deal with all to often I am trying to piece together for you a scenario of whats been going on with your car but the problem with this is, you don’t know what was used on your car, were they Aftermarket Catalytic convertors or were they Subaru Parts?

      Same thing applies for the 02 sensors. If Cheap aftermarket parts were used than absolutely it will just continue to be a problem time after time until O.E. Subaru parts are put back into it.

      If its had O.E. Subaru parts, than it has never actually been diagnosed.

      They way it should work is the check engine light comes on, the car is diagnosed and the code number and cause of the code number clearly noted to you on the paperwork, the car is repaired the light goes out and does not come back on for the same code number within a years time at best, if ever again.

      The light may very well come back on for a different code the next day and be unrelated, and that does in fact happen.

      As long as their is clear communication abut what code is set and when, followed up with clear direction for corrective action, this action done by a good shop with a capable technician, you should have good results.

      Anything other than what I have just mapped out with yield frustrating results.

      Hope that helps


  75. Hi Justin, thanks for the great insight into the subaru world. I live in Uganda, East Africa. Mine is a Subaru legacy 1998 BH5 EJ 20 model. I bought it second hand after it had done like 100,000 kilometers. While driving to the countryside, i drove it on Gear 3 and not D (its automatic). It had an engine knock as a result and engine was replaced but Check Engine light is constantly on, OBD2 check gives error code 91 – TCS Relief Valve. No subaru service center here (even the authorised dealer) is able to give me the correct diagnosis for the problem, am reluctant to just drive around with a constant Red warning light (now 2 months since problem started)Please help.

    1. I drove it on gear 3 to give it more power as it lacked and could not pick up speed as my previous subary legacy did. A local subaru dealer replaced 1 sensor in the sump and now power is ok but Check engine light in RED still persists.

    2. Hi Bryon,

      Thats a model i am just not very familiar with as it was never available here in the US. I suspect that the “Torque convertor cut solenoid” is stuck.

      What needs to happen is the transmission pan needs to be removed, the solenoids tested and inspected as a step one, in the diagnostic process. There will be a resistance range the component should test within, I don’t know the value as I don’t have a service manual for that model, but thetas what needs to happen to get to the bottom of it.


  76. Justin, what a wonderful blog…We are new Suburu owners just today after purchasing a brand new 2012 Tribeca in Perth, Australia.

    We picked it up from the dealer at 5.30pm with only 110kms on the clock, drove it home, parked it up in our carport, then 2 hours later popped out to the shops to find it made a big “clunk” noise, lacked power and all the CEL, traction, cruise control lights etc. came on. We thought immediately we had bought a “lemon”!!!

    I then googled for 2 hours online for solutions….we checked the gas/fuel cap was tight,it was but we tightened it as much as we could, no result, then I read somewhere that we should disconnect the negative battery lead and reconnect it and guess what, this worked much to our relief!!!

    Should a brand new car straight out of the dealers yard be doing this? I am just chasing your thoughts. We are going to call the dealers first thing in the morning. We have only owned the car for 6 hours!!!!

  77. I disconnected the green connector under the glove compartment and all the problems solved. (no flashing CEL, no cooling fan running before starting the engine).

  78. I’ve just barely broken the 30k mile mark on my 2009 forester. My check engine light has been giving me hell being on sometimes and off others. After a while I stopped taking it to the mechanic because, let’s be honest, trying to “save the environment” is an expensive hobby when your light comes back on about once a week even after you do bring it in. Today I tried filling it up at the gas station and it spewed gas back at me (yes it did need gas and no the gas sensor isn’t broken). I drove it home and stopped by a local mechanic who said he’d look at it Monday. Thing is that my check engine light turned off on my drive home so I went back tot he gas station and filled up without trouble. My question? How do I disable it. I know you’re not supposed to but seriously. YOU aren’t going to pay for it and even the local subaru dealer hasn’t resolved this perpetual issue. When it gets to the point that some retarded sensor or another is making it so I can’t even fuel up?! I’m done with it. How do I turn this crap off completely?

    1. Glenn,

      Come on man!

      The 2009 Forester is under warranty.

      The OBDII system is beyond your Comprehension, which is why some one that understands it needs to be involved, I have written 2 articles on this and it still didn’t reach you, which is ok, its just like I could read 2 articles on quantum physics and still not grasp it.

      When I read “your mechanic” and “trying to save the environment is expensive”, why are you paying to have it looked at when its under warranty? I dont know how I am supposed to take comments like this seriously.

      You cant disable OBD and you dont want to, its like never checking your blood pressure for fear it may read to high. Get over the fear, and have it resolved or it will actually start to cost you real money. Do you honestly believe that every 2009 Forester must some how exhibit the exact same situation you have?

      Its not safe to have a car “Spew Gas” Ever heard of fire?

      Take a breathe, seek out a pro with answers and resolution to the current dilemma and go there! Or dont and buy a horse, but regardless for your own safety do something different than you have been doing or dont expect a different result..

      3 yr 36k bumper to bumper warranty
      5 yr 60k power train warranty
      8 yr 80k emissions warranty


  79. Thank you, thank you and boy, do I feel stupid. For the first time ever, I hadn’t tightened my gas cap properly and you’ve just saved me another mechanic’s cost on my beloved 10 year old Subaru. Unfortunately, I’d previously taken my car to Walmart for an oil change and now need a new oil pan. Thank goodness I’ve now got a good, honest and reliable mechanic, and found your website!

  80. Justin,

    Thanks for all of this great information. I’ve been reading a number of these posts and have found the information very helpful. I do have an issue that is very similar to a number of the posts already submitted, but perhaps a bit different. I have a 2002 Subaru Legacy Wagon with 140,000 miles. I bought the car with 38k on it and have been driving it since 2005. The car was originally purchased in PA (salt belt state) in 2005 I moved to Montana that year and that has been where most of the miles have occurred. In 2009 I was getting several codes that indicated a problem with the 02 sensors so I replaced both of those with Bosch sensors.

    The codes during that time were:
    P1507 – Idle control system malfunction (fail Safe)
    P0303 – Cylinder 3 misfire
    P0171 – System too lean (bank 1, sensor 1)
    P0031 – Ho2S Heater control circuit low (bank 1, sensor 1)

    After doing a little research and consulting my Chiltons manual I figured the new o2 sensors and new spark plugs and wires were the best course of action. I was able to do all of that for about $200 and got all of the codes cleared except P1507.

    I took that sensor off and cleaned it as well as replaced it gasket a couple of times and have still not been able to clear that code as of today.

    The biggest problem I’ve had recently is that the P0420 code which was pending for quite awhile and I was ignoring (bad move on my part) has now been active for probably a year. I’ve noticed over the past year or so my car has been accelerating extremely poorly and seems to be starving for air.

    Codes as of today are:
    P1507 Idle control system malfunction (fail Safe)
    P0420 Catalyst system efficiency below threshold
    P0065- Air assisted injector control range

    At this point I’ve taken off the Cats and the entire exhaust from the manifold on back and am in the process of replacing it all. When I took off my o2 sensors I noticed that they had a light tannish almost white deposit on them. Based on what I’ve read that might indicate a leak in coolant internally, a problem I found out is a recall issue for my vehicle. Apparently I was supposed to have a coolant conditioner of some kind run through the system, however I did not know about the problem until yesterday. I have not noticed a significant decrease in coolant levels though.

    I also believe my problem with the catalytic converters could be attributable to excess corrosion of the under carriage, another recall for my vehicle as it was in the salt belt at purchase, (MT didn’t help that matter either.)

    At this point I am just waiting on some of the parts to come in so I can install the new exhaust. I currently have Walker Direct Fit cats ready to install and a walker muffler and remaining exhaust from the cat on back so there will be no problems with it not fitting hopefully. I had planned on only replacing the cats however the flange between there and the lower end of the exhaust was so corroded I couldn’t get an air tight seal, so I opted to replace everything except the manifold.

    I guess my questions to you are should I keep this after market cat system? Do you know anything about Walkers? They have a 25,000 mile function warranty as well as a 5 year structural warranty. The parts are described as using OE style fits and using a higher loading of precious metals so the check engine light won’t activate…. is this just a bunch of BS? Do you think I should drop the extra 300 for OE cats?

    I guess I’m also wondering if I have the internal coolant leak described above, won’t my new cats plug up and foul up the sensors. Should I also install new sensors with the new cats?
    So far I’m in about $700 on this repair.

    I love my subaru and would like to think this is all worth the effort.

    If I lived in Seattle I would just bring you my car, however now I’m living in Arizona.

    1. Hi David,

      “P1507 Idle control system malfunction (fail Safe)
      P0420 Catalyst system efficiency below threshold
      P0065- Air assisted injector control range”

      So first of all if you use an aftermarket catalyst then you will do it twice, regardless of any claims Walkers may make, if you read enough post here you will find that statement backed up by other drivers experiences. Same thing goes with the 02 sensor and spark plugs, because you mentioned $200.00 as the parts price I know you did not buy O.E. Parts. You may not need a Catalyst you my just need the proper 02 sensors since the code wasn’t there before. Why don’t you give this a read.

      There is not enough precious metal in the aftermarket Cats to last, so they don’t and that’s why they are less expensive. By the way you do not have to GO to Subaru TO buy O.E. parts, you just have to figure out who makes it for Subaru and buy that. For Example NGK makes the Spark plugs.

      The 1507 tells me you most likely have a manual trans equipped car and some testing of the neutral switch circuit is required.

      Hope that helps


      1. Justin,

        Thanks for your suggestions. I’m going to ditch the Walker Cats and see if I can get an OE replacement this week. I wasn’t too attached to that replacement anyway, whoever welded it forgot to plug one of the bungs for the upstream sensor and melted some of the filter inside with spatter.

        I will get 1/2 way to an OE with the exchange and this will greatly reduce the headache down the road, so I thank you sir for in advance for saving a great deal of hassle and money down the road.

        So the 1507 is an electrical issue related to the transmission? I’m going to take my car to a dealer in Tucson when I get everything back together, so I will have them check on that.

        thanks again!

        1. Justin,

          Thanks for the info and link.

          I have another unrelated problem that I’m wondering if you’ve ever had any experience with. When I turn on my A/C and run it for extended periods and in particular when the temp outside is in the 90s my blower seems to make a strange honking noise. It does this often when I’m at a light or idling.

          Could that be caused by overfilling the system? The A/C still blows cold air, but that sound can’t be good.

          1. If the noise is from the blower motor it isn’t related to the AC system behing overcharged, it may be the bearing in the motor or something else.


  81. Great job Justin!

    Reading through the questions and your responses, it appears that often the CEL light turns (for emissions) on after having head gaskets changed. I have seen a few suggestions to have the ECU reprogrammed when this occurs. Does reprogramming the ECU reset its historic data to compensate for the fixed engine (as in settings, not the actual programming)? I can’t imagine reprogramming the ECU will do anything unless it is actually new/updated code OR if reprogramming it means resetting its historic values and forces it to start using new ones for the fixed engine.

    I have a 2003 Legacy of which I just had the head gaskets changed and within 1 month of this my CEL light is turning on (they told me it is for the cars emissions – sorry, I did not get the code as I have only just started researching this since the CEL light keeps turning on). My shop has checked the sensors/replaced the gas cap/etc… over the past 1.5 months but the CEL continues to turn on after 20 cycles or so of being reset (week and a half). The engine is running fine and smooth. My shop has asked me to get the ECU reprogrammed. I’m not convinced this will do anything unless it has something to do with the engines historic limits based on the previous head gaskets/performance limits. Your thoughts?

    1. Darren,

      Cant offer much without the code, I assume its a Catalyst code. There may be a Reflash for your car, is the shop that did the head gaskets not capable of this?

      Most shops should be able to do this unless they have not invested in the Subaru Select monitor, and if that’s the case maybe they should rethink the whole Service Subaru thing.

      A reflash in some instances changes the parameters to which the ECM may trigger a fault code.

      Hope that helps


      1. I checked with my shop and the two codes that keep showing up are P0440 and P0442 which had something to do with evaporation (gas vapor escaping/gas cap issues). He said they have checked the Catalyst and it is fine (he mentioned the code for it identifies that the Catalyst is working less efficient then it should be and my car has never shown that code). They also checked the O2 Sensors which were fine (P0030, P0130, and P0131 which have not shown up in my car either). I asked why they were not able to reprogram the ECU themselves and he said Subaru Canada won’t give the software out unless you are a certified dealership. He said in the States any one can get it but up north, Subaru Canada is much more strict on who can do it.

        I have never had the ECU flashed before in the car so if Subaru did release new software for it in the past 9 years, maybe it will help. I’d feel better if I knew the software did have updated parameters. If they don’t and it is going to be a reflash of the same program/parameters, I see little use in doing this (and I’m sure the dealership will gladly take my money and do this). Do you know anything about the ECU programming used in Canada (assuming its the same as the States) and if there has been a new release of software in the past 9 years for the 2003 Subaru Legacy Station Wagons?

        1. Hello Darren,

          P0440, 442 dont always mean gas cap, any Evap leak will set it.

          P420 is the Catalyst code, is that being set? 02 sensors do not necessarily need to set a code to be slow and in need of replacement

          As far as the data files I have never heard that about SOC. Its actually illegal in the US for the manufactures to withhold the information unless its a recall. Unless the files are different the us files should work.

          Almost every Reflash contains new parameters that’s the point of the reflash, as Subaru comes to an understanding that in the field certain conditions pop up that were not anticipated.

          Reflashes are very important just like a firmware update is for a modern computing device.

          Hope that helps


          1. Just a follow up that I had my ECU reflashed 3 weeks ago and have not had the CEL turn on as of yet (fingers crossed). The last code I had when getting the reflash done was the Evap Leak (again) of which I’ve just been extra careful to extra tighten the gas cap each time I fill up. So far so good. Thanks for the advice.

  82. Hey! This is my first visit to your blog! We are a team of volunteers and starting a new project in a community in the same niche. Your blog provided us beneficial information to work on. You have done a extraordinary job!

  83. Hi Justin,

    I have a Suburu Forester MY09. Whilst in warranty the car stalled x3 and the engine/ cruise lights also came on the dash. The end result was there was loose connection, which fixed the stalling issue.

    Two weeks later the engine lights would appear and then disappear. Then the returned with the cruise control lights and remained on the dash. I took it back to Suburu and they reset the computer though did not diagnose an issue. A week later the lights came on again. If I travel > 110km/hr the lights returns.

    Suburu advise me that the converter compliance needs replacing. The car is now not in warranty (1mth out) and Suburu say it is a new issue> Though this occurred when I first took it to the dealers whilst it was in Suburu. They Just reset the module and of course the lights went away.

    Does it sound like a new issue, or a problem that was not fixed when it was in warranty?



    1. Hello Kate,

      This is the problem I point out most often, you only know the light was on but not the code number, without a code number its not possible to answer your question. The light can come on for any one of several of thousands of reasons.

      If you had a Catalyst code before the warranty expired then you have a case to make with Subaru, but if it was a knock sensor code you don’t. Check you receipts for code documentation, if there is none call the dealer and ask what code’s have been set on what dates.

      Hope that helps, and from here on out any time you take it in for a check engine light ask what code was set!


  84. Hi Justin, I’m all the way over here in Kenya, East Africa. I have a ’99 Subaru Forester S/tb ex-Japan (most cars here in Kenya are Japanese used imports). A couple of months ago my CEL came on briefly, then went out again. Over the last couple of months it has been doing this from time to time, but the light never stays on for more than a few seconds and may not come back again for a while. I have had the car for 5 years, and always take it to the same trusted mechanic. He says that I should not worry too much as it may be the sensor is stuffed because of the low-grade fuel we sometimes get here in Kenya. The spark plug leads and spark plugs were replaced about 3,000 miles ago. The car’s performance is still great, although the gas mileage seems to have gone down from an avge. of 9.5 kms. per litre before, to about 8 / 8.5 kms. per litre now. The exhaust tailpipe deposits are quite black, not grey. I have seen on another forum that I might be able to re-set the CEL / rectify the problem by a) disconnecting the battery for 5 minutes or b) removing the ECU fuse for 5 minutes. What would you suggest? I look forward to your answer. Of course, I’d be happy to bring the car to you – if I lived in the U.S. !! You seem to know what you are talking about. Thanks, Mike

  85. Dear Justin,
    I have a 2003 Legacy Outback, with ~120000 miles on it. Recently the check engine light has started to turn on. The code is P0457. So far my mechanic tried changing the gas tank cap, some solenoid in evap system and also searched for leaks using some kind of smoke machine. Could not find anything. The light stays off for a while, but whenever I drive long enough on the highway, the light comes back. Same code.
    Thank you in advance for suggestions.

  86. Again, thanks for your most thoughtful reply. I see the difficulties faced by a shop owner in this situation. I will discuss with my mechanic (trusted, many years working on our vehicles) the time/cost factor in diagnosing this particular issue and go from there.

  87. Good morning,
    My 2003 Forester CEL is on, just checked with my independent mechanic and P0420, P0519, and P0030 come up as well as B0519. Reading this forum it is not as clear as he stated that the catalytic converter must absolutely be replaced as well as the air sensors, etc. for a total bill that will make me do a keep-or-replace decision. Are there intermediate steps he can do to verify his diagnosis? The car gets good mileage and is peppy. I wonder if there is something in the exhaust system that is affecting these codes. Any advice?
    Many thanks for your time and expertise.

      1. Thanks for the reply. I do want to keep the Forester. To refine my question: with multiple codes, is there an order in which you look for problems, wait, and reevaluate before swapping out parts as my mechanic wishes to do (that is, swap them out)? I will read the p0420-explained page.


        1. Hi Betsy,

          Each situation in dealing with multiple codes is different. The situation based on data analysis, inspection of components and known common problems are all things tools that should be used when evaluating a car.

          Sometimes swapping in a known good component is the only way to prove or disprove a working theory if the testing doesn’t not yield a automatic go/no go type of a scenario.

          P0420 can be very difficult for some to diagnose without a Subaru Select Monitor III, most general repair shops would not spend the money on a brand specific OE level tool. Not having the right device may make it more difficult to diagnose than if you did. There are convertor tests that can be done as well, but the select monitor gives you the same type data the ECM is seeing to set the code and light, this should be done in correlation with other tests.

          There is an order but there is no “Rule”. Most see a P0420 and automatically assume catalyst and 02 sensors, we have actually seen cars that have had the cats and 02 sensors replaced at a dealership or general repair shop and still set the code, as there was never an actual diagnoses done. I have yet to see a code scanner that can tell me that a mouse ate partially through a intake manifold harness under the intake manifold causing intermittent voltage issues with sensor data back to the ECM.

          The market place in many cases does not allow for proper diagnoses. One code is a simple diagnoses the next is complicated, auto parts stores offer code scans and as a result that devalues what a shop offers and we now have drivers that don’t want to pay for a diagnoses, how much time does a shop put into a free diagnoses? Even worse is that not every diagnoses is Conclusive!

          Our shop charges for a diagnoses based on what we went through to get results, and as such we have drivers that don’t bring their car to us. We typically try to waive the diagnoses when making repairs even though it hurts when we do. We don’t suggest to replace parts that we can prove as failed typically, but I am aware that other shops do, again mostly based on what the market place has created.

          Is this any one persons fault? No but its the state of the industry. There are pockets of shops that will buck the trend, you may not have your car at a shop like that and you may have a car with a situation lending itself to a much more difficult diagnoses.

          Thats really about all of the light I can try to shed on your Subaru and is codes.


  88. Hey Justin,

    Thanks for sharing what you know with us. I haven’t yet made my way through all 500 comments, but I have a quick question for you. I’ve noticed that the CEL on my 2000 Impreza won’t illuminate at all, even when the ignition is in the “on” position. What do you think?



  89. Hi. Apologies if my check engine light issue has already been responded to in the almost 500 replies to this article; I have not read them all. I have a ’99 Impreza at about 134K and with mine the check engine light has been blinking then stays off. To my knowledge it has only done it twice – yesterday and about a month ago. I was thinking a code reader may not work in my situation because the light isn’t continuously on (?). I initially thought it was my spark plugs because that was what it was for the hyundai I had previously but I changed them after it 1st happened and now yesterday the blinking occured again. Any advice would be greatly appreciated.

    1. Lance,

      With out a code number there is little I can offer.

      The blinking check engine light means STOP DRIVING IT until its diagnosed and repaired. Please consult your owners manual for any clarification about this.

      The code will remain in memory for a bit after occurrence so yes a code scan is a fantastic idea and the next step

      Hope that helps


  90. Sorry to keep posting… The problem is intermittent. runs great at start up (rich?) then intermittent after normal op temp is reached.
    Sorry you have have to drag all the info out of me…

  91. Hi Justin,
    I think the stress of car and late hour of my post caused me to babble incoherently. Will now clean it up. Bought 2000 Forester w/CEL on. HG and timing belt replaced by previous owner. Code when I bought it was o2 zone 1 and Cat. Replaced o2 and codes went away. CEL came back on codes misfire cylinders 1&3. I installed new plugs, wires and coil pack. Still missing. Took to “Independent Automotive Inc.” in Sparks Nv. They advertise as Subaru specialists. IAI inspected timing belt, gears and valves. Told me valves were loose and hadn’t been adjusted properly after HG replacement. Paid $712.00 and drove it home. CEL came back on after 30 minutes of driving. Cyl 1&3 misfire. I am going to replace injectors 1&3 next.
    Hope that clears it up. Your insight is greatly appreciated.

    1. Before you spend money on something that isn’t going to fix it, drop the exhaust and look at the Valve guides, its very common, fuel injector failure on a 2000 is not, and would only be intermittent if it was a restricted nozzle which would be resolved with a cleaning rather than buying all new.

  92. I bought 2000 Forester a few weeks ago with the engine light on. Had codes for o2 sensor, Cat & misfire. New o2 sensor cleared all but misfire. Took it to a Subaru mechanic and they visually inspected timing belt and gears. New belt and head gaskets 8k miles ago. Mechanic adjusted valves and installed new valve cover gasket. Compression tested 155 to 170. Smogged ok. 1k in repairs so far. Light came on again the night I got it back. Misfire is sporadic NOT constant. I installed new NGK plugs, wires and coil pack. Any Ideas?

    1. Hi John,

      Some of this doesn’t add up, so 8k ago the HG was done which would have included new Valve cover gaskets and a valve adjustment if done at a good shop. But those things were just done again?

      Most likely the Valve guides have dropped, you probably should not have bought a car with a check engine light on and especially with a misfire code. You can read here

      Hope that helps


  93. Hi Justin,
    This website is awesome! Amazed at the quality and care in your responses!

    I have a 1997 legacy 2.2 wagon. I bought it from a young lady who I think had the check engine light disconnected. I didn’t realize it when I bought it, but it probably related to a catcode 0420 that comes up (multiple mechs suggest o2 sensor failing)(car passes CA emissions test); my guess is that the girl may have done something to fudge the visual inspection when she smogged before selling it to me.

    I want to sell this car as it’s now an extra vehicle. My question: Are there any ways to check the CEL bulb before I dissemble the dashboard? Looking through this page of posts made me hope that there might be a simple connection to check first under the dash, perhaps seeing if the girl disconnected the wire from the ECM…

    My intention is to fix the CEL and repair the catalytic convertor, take care of the issue I unwittingly inherited….

    Thank you in advance

    1. Hi Dan,

      If the light fails to come on when you turn the key to the run position, most likely the bulb was pulled.

      Its actually going to take you less time to remove the cluster and replace the bulb then to try and see if someone cut a wire. The average person is not savvy enough to locate the the wire form the ECM to the Printed circuit. While your at it I would replace the main illumination bulbs in the cluster as well as there will never be a better time to do so than when the cluster is already out.

      Hope that helps


      1. Awesome, thank you for the quick response. I’ll dive into the cluster, but can you recommend any manual or another? I’ve seen what can happen when dashes aren’t taken apart carefully, hoping to avoid similar mistakes…

  94. Justin,

    I was wondering if you have some advise for me even though i do not currently have a cel on. I have a 2003 Baja and i recently noticed that when i fill up with fuel i will occasionally (only noticed it when i fill up at 1/2 or below)get a lurching/surging feeling from the car. When this is happening, i watch the tachometer and the gauge goes from 3000 down to 800. It has stalled on me once while this was happening but restarted right away. Normally it happens within the first 5 miles after filling up the gas tank and then will run fine until the next fill up.

  95. Hey, so I have a 2001 Subaru Forester, and the check engine light has been coming on since my aunt had the car, and she bought it new. She had taken it back to the dealer and had it “fixed” but I think all they did was reset the computer system, and it came back on.

    Now I own the car, have taken it to autozone and the read out was that the problem could be one of three common problems, a catalytic converter, a knock sensor, and a loose gas cap. Well, I replaced the gas cap and sensor, and refuse to replace the catalytic converter.

    This car always passes emissions and safety inspections every year, provided I disconnect the battery and drive the car for one hundred miles. Unfortunately, soon after, probably about 50 miles after, the light comes back on.

    I have been told by multiple mechanics that it is simply a computing error, which many 2001 foresters have actually had. I was also told the best solution to this hassle is to get a new car, which is out of the question as I am currently a college student.

    What is your take on this situation?

  96. Hi Justin,

    The Check Engine Light on my much-loved 2002 Outback just came on for the first time ever this morning. The car had not been run for three days, and it has been wet and snowy (nothing new for here). The car was idling while I cleaned off the windows and after I had driven for about one block, the CEL came on. It stayed on for a few seconds and then went off. I turned around to go back home, and it came on twice more, for about 5-10 seconds each time.

    I’m an older, single woman on a fixed income, so I don’t want to take it in if I don’t need to (I always go to Subaru), but I can’t afford to damage the car by driving it when it shouldn’t be driven.

    What do you suggest? The gas cap’s on tight; the only recent “change” is that I just had my stereo and speakers replaced (it was broken into last month while it was raining and apparently two of the speakers got water damage). Could the installers have inadvertently done something to cause the light to come on now?

    Thanks for any suggestions you can give me.

    1. Hi Susan,

      I would suggest buying one of these,

      So you can check the code your self from now on, because with out a code number there is no way to know gas cap VS crank sensor code, one will leave you stranded and one wont. IF you can use a tv remote control you can learn to use a code scanner. I personally believe its now a necessary part of modern vehicle ownership.

      Sorry I cant offer more, typically if its running alright its ok to drive somewhere to at least have the code scanned.


  97. I have a 01 outback vdc 3.0. Is there any way to adjudy the idle? Ot is to low and continues to stall. The cel is also on and is a misfire on 1, 3, 5. Have changed all plugs and boots. Thinking about replacing the coils next. Is 1, 3, 5 on the passenger side?

    1. Raising the idle wont help, if you continue to drive it with a misfire you will damage the Catalyst and possibly the engine.

      Because you have multiple misfires on the same bank you need to look into things that affect the entire bank, and not assume that three coil packs failed. This could include an intake manifold gasket leak or timing chain/guide issue. It really needs a good evaluation.

      Hope that helps


  98. Justin,
    Love your work. I have 2001 H6 Outback which developedm CEL and VDC lights after I cleaned the engine prior to an inspection. I just had a local Subaru centre do a scan and they reckon it is o2 sensor 1 bank 1, and wanted to charge me over $700 for one, plus labor. I naturally told them to shove that.
    I am asking what is a good OBDII scanner to acquire, and best source for 02 sensors? I picked up that is a good source, but many OBDII scanners I have searched say they may not be suitable for Subaru.

    Any comment?

  99. Hello Justin
    My 2000 RSK B4 Legacy had a battery warning light.I replaced the alternator with a genuine one from another engine and power problem solved.

    I drove less than 10Km and BRAKE WARNING light appeared on dashboard followed by flashing CHECK ENGINE light.BATTERY WARNING light is back but car is running great.
    What could be the problem here?
    Can low brake fluid trigger both BRAKE WARNING and CHECK ENGINE lights?
    The car was immediately parked.


    1. The Vehicle needs at least a code scan for the check engine light and take things from there.

      With out a code number there are a hundred places to look.

      The low brake fluid in the US models cant trigger a check engine light, cant speak for where you live.


  100. Greetings Justin — 2002 Forester w/112,000 miles. CEL with no codes & unable to communicate with the ECM. It was told to get ECM Flashed. MPG will range from 13 to 26. CEL is constant upon startup. Emission testing station is also unable to communicate with ECM. I have a appt scheduled with dealer. Any suggestions on Flash. Thanks — Joe

  101. Hello Justin
    I just bought a 2000 Subaru Legacy RSK B4 with Twin turbo and has done 95750KM.
    First battery light came ON then engine cut off.Replaced alternator and battery light is gone.Drove about 10Km then brake signal came ON on dashboard.Few minutes later CEL started flashing about twice a minute.Car is driving very well but I parked it immediately.
    Kindly advise,thanks.

  102. A couple of months ago my engine light came on in my 97 impreza 150,000 miles. I took it in and was told I had a P0325 knock sensor code but that it wasn’t critical. Shortly after I moved and started driving less. When I did drive the light would sometimes be on and sometimes be off. At the end of February I will have to do a big chunk of driving so now I am wondering should I have the code further investigated or is it minor as my mechanic described?
    I would appreciate any advice you have to offer! Thanks!

    1. Hello Elizabeth,

      I cant really know nor can you if its the same code or something new, but the knock sensor will not correct it self, the mechanic was very incorrect in telling you it wasn’t a big deal.

      the knock sensor is there for the fine tuning of the ignition system which affects engine fuel economy and overall engine longevity as well.

      Think of it like this, if you choose to not brush and floss your teeth they don’t fall out the next day, but this bad habit over a period of time will increase the chance of big dentist bills and undesired results.

      Ignoring the knock sensor wont ruin the engine the next day but over time the combustion process wont be as precise and as a result will be undesirable as well.

      A 1997 Subaru Impreza with the 2.2l is really a good car and will last for a very long time in my opinion one of the best Subaru ever built, take the best car of it you can and it will take care of your bank account.

      I would start with a diagnoses, and if still the knock sensor replace it and take things from there

      Hope that helps


  103. Hello Justin,

    I bought my ’99 forester last spring. The head gaskets blew two weeks later 🙁 Had it fixed, but they told me that the piston rings weren’t in the greatest shape. It burns oil (+/- 1qt per tank of gas), but if I keep oil in it it runs smoothly. The CEL has been on solid for about 4 months, I had the code read and they said it was an O2 sensor. Last weekend I took it for a longer trip (7hrs round trip on the interstate). On the way home we stopped for gas and then the CEL started flashing for ~30 sec then went back to solid. The next time I started it up, same thing, flashes at start up then goes back solid. There is plenty of oil in it. No blue smoke. Runs smooth. The gas cap is on tightly.
    Any thoughts?
    Thank you!

    1. A Flashing check engine light indicates a cylinder misfire, you need to have this evaluated to determine the cause. You have 4 cylinders so a possibility of 4 different misfire codes, from there it could be a plug, plug wire, fuel injector, etc.

      Worn oil control rings are not the end of the world as long as you keep oil in it.


  104. Hi Justin,

    I have a 1991 Subaru Legacy which has been meticulously serviced and looked after over the last 15 years. The check engine light came on about 4 days ago and it has been difficutl to start the car since. It takes about 7 – 8 turnovers to get it started whereas before this it used to start first time every time. Any help or suggestions would be much appreciated!


    Big D

  105. Hello Justin,

    I do have a question, and the shops can not tell me what exactly is going wrong with my car. I have a 2002 impreza wrx 2.0L Turbo. i had the CEL for p0171 bank 2 system lean. It was a faulty MAF, then as soon as i replaced that it was fine for 3 days, then the CEL came back on but for misfire codes for all four cylinders, p0301, 302,303, and p0304. The spark plugs were replaced last April with stock ngk platinum, but I checked them again just in case the tips were burnt, no issues so I cleared the codes and my car ran fine, plugged in the OBDII and it was throwing a p0420 without the CEL actually coming on. So I left it alone, then the dang CEL came on when the gas tank was at half a tank and stayed on until I filled up again throwing p0171 bank 1 system lean and the gas cap has been replaced in November 2011 when I did my oil change. I Put in premium gas because of the turbo and the oil is full synthetic so I take care of it very well. but I can not find a vacuum leak or bad o2, and its not throwing a fault for the same codes consistently. can you throw some ideas out to me. I have replaced the rear o2 sensor, turbo boot, purge valve, timing belt, spark plugs, maf, fuel filter, and all this has been done within the last year.

    1. The bank 1 and 2 lean codes could indicate a front 02 sensor other wise called a front air fuel sensor. This should be evaluated first. I would also put back in NGK platinum spark plugs you cant see the ignition pattern noise aftermarket plugs cause with your eye.

      I am not saying replace the front air fuel sensor, I am saying the data needs to be evaluated.


  106. Hello again.

    I have more news. My son tried the scanner tonight on a Buick Century 2003 and it worked. This is really strange. My Subaru 1998 and the Toyota 2007 are OBD11 compliant. They should be able to use this scan tool. There has to be a problem somewhere.

    The Actron website and other websites say that the cp9580 scan tool works with my 1998 Subaru. The scan tool shows on its screen the menu for domestic, European and Asian cars. It does not make sense.

    I hope Canada is not the problem. I’m assuming that my Subaru which was built in Indiana and bought in Montreal came to the Canadian dealer as built by US specifications. Gee, I hope that’s not the problem.


  107. Hi, Justin.

    Thank you for the quick reply, much appreciated. My son just tried the scanner on a 2002 Lincoln LS and it worked. Then he tried it on the Toyota and got the same Error Link. What could it possibly be?? BTW, we’re in Montreal, Canada.



    1. Lance,

      I already told you to try a different scanner, you can also contact the manufacturer for help. I dont support their product and have no idea why you are unable to make it work.


  108. My 95 legacy wagon, manual transmission non turbo. When driving at a sustained speed it will get jumpy, almost feels like it is running out of gas. This doesnt happen all of the time, but it does happen in any gear. Also after parking it will give a smell of burnt rubber. I also noticed the temp gauge is stuck and am assuming the thermostat is stuck. Any suggestions?

    Thanks so much for the blog, you are a rockstar!

  109. Hi, Justin.

    I have an Actron cp9580 scan tool that fails to communicate with my ’98 Subaru. I tried it on a 2007 Toyota Carolla and the same problem. It attempts to communicate, then it leaves the message: Link Error. I followed the manual to the letter but no luck. My Subaru dealer used their scanner on my car about 4 months ago and replaced the knock sensor. Then they erased the code. Two weeks later the check engine light came back on. 4 months later, it just went off. I’d like to know why my scan tool does not work. Appreciate any help you can provide.

    Thank you!!

  110. Hello- I just replaced the catalytic converter on my 2001 Subaru Forester because it was throwing a P0420 code. A day after the repair, the Check Engine Light returned, throwing code P0325 for knock sensor. Did one issue cause the other- or was this improperly diagnosed? I’m wondering if this is something that the mechanic should have identified prior to replacing the cat conv, which cost me a pretty penny.

    1. If you read the article carefully you will see that in some cases if the light is on and a fault code set, the monitoring system for other systems are no longer monitoring those systems thus any pending issues are unknown by you or the shop. Both P0420 and P0325 are very common codes for the Subaru, I suspect no foul play or incompetence only a 11 year old car.

      The catalyst was expensive the knock sensor not nearly so.

      I hope that helps


  111. Hello Justin,

    Thanks for your help in advance. I drive a 2002 Subaru Forester L 5 speed manual. A few days ago I noticed that my car “lurched” and “jerked”. Thinking that was weird but didn’t pay too much attention to it as I thought maybe I left off the clutch to quick or something.

    The next day I get into the car and my speedometer, odometer and trip were not working at all. Once, however, while driving either in 3rd or 4th gear, I noticed that “lurching” again (either from the tranny or engine…don’t know) and my speedometer was going crazy! Another time I noticed, while parked, that it was going crazy, too! This only lasted 10 seconds or so.

    I took it to the folks at AutoZone and I got two error codes; P0500 and P1540 – Speed Sensor malfunctions.

    Now, I’ve been doing some research around the web but can’t find anything too helpful. I could replace the speed sensor but given the “lurching” that I’ve experienced it could actually be a worm gear gone bad inside the tranny.

    From your experience, what can you tell me about this issue? How should it be diagnosed? How much could repairs cost for different options?

    Any help would be amazing! Thanks!

  112. Hi Justin,

    First of all, holy crap man! You have answered a lot of questions! Thanks for all of your advice!

    I drive a 2002 Subaru Forester, 5 speed manual. Very recently my speedometer, odometer, and trip had all quit. I believe that when it quite I was in 3rd gear and I felt some lurching going on or some kind of hesitancy from the engine/transmission. I am also getting a P1500 and P1540 (speed sensor codes). Every now and again over the past couple of days I have noticed that my speedometer would flicker from 0 to 60 very rapidly and then die again. Once this happened while driving and the other time while parked. When it happened while driving I felt the lurching of the car. In addition, when the car is cold in the morning, I will turn on the car and the RPM will go pretty high (up to 4500) while idling before coming back down.

    As I understand it, there is a gear inside the transmission that can go bad and may need to be replaced. Is that the case? Or would it be the speed sensor itself and, in effect, causing issues with the IVAC and Fuel pump? If I had to drop the tranny, how much are we looking at price-wise?

    Thanks for your answer in advance!

    1. Hi Andrew,

      Thats one I really would have to see to know whats going on with it for sure.

      Anytime you have a VSS issue the car will act up, but it could be the sensor, the gear or the wiring. There is no way to know with out evaluation of the vehicle.

      Sorry I cant offer more.


  113. Greetings Justin,
    Thanks in advance for any advice you can provide. Your site and your free advice is admirable. I have a common problem on a unique car. Three months ago, as a gift for my 16 year old son, I purchased a 1998 Subaru Legacy GT Limited from a private party (a subaru mechanic). The mechanic had replaced the original engine with a subaru ej22 (2.2L) engine. In hindsight, I now realize I should not have bought this car for numerous reasons, but because the owner stated he was a subaru mechanic, I was not as cautious as I should have been, and I did not get the car checked. Anyway, the car has had several mechanical problems (bad caliper and leaking valve cover gaskets) which were fixed at my local subaru dealer. However, I have a continuing problem with P0303 codes (cylindar 3 misfire). Dealer says plug, wire, and ignition coil are OK. They performed some kind of $90 engine maintenance service that supposedly cleaned the injectors. The car ran for about 200 miles, then the P303 code appeared again (I have my own code reader). My question is what should I ask the dealer to do next? Is is harder to diagnose problems on this car due to the engine replacement? Thank you Justin.

      1. Thanks for reply Justin – Let’s assume for the moment that sticking valve(s) are a problem with this engine. Could sticking valves destroy the engine? Is there something that can be done to keep the problem from getting worse? For example, is there any kind of additive (to oil or fuel) that would help mitigate the sticking valves, or would I do more harm than good by fooling around with additives? Thanks for any further advice.

        1. There is no simple answer to that, a sticking valve will cause a misfire, and over time misfires can cause engine damage.

          Best way in the car to alleviate sticky valves is with a fuel induction cleaning to try and remove some of the carbon from the back sides of the valves and the stems.

          Hope that helps


  114. Justin, you’re a total legend. cheers for any help you can give. I have a 2000 TX Legacy, about 175,000kms on the clock. CEL has been coming on when i hit big hills, cruising down the other side it goes off. Its just come on recently and stayed on. Otherwise the car is running fine. Any thoughts, or just the regular emmission issue?

    1. Gibbsy,

      Thanks for the kind words. Without a code number I am guessing here but I suspect a boost or boost monitoring issue since its a TX and I do believe that to be a Turbo model ( wasn’t available here in the US)

      If you can gather a code number I might be able to offer a bit more.


      1. Hey Justin
        Thanks for replying. I’m writing from the otherside of the world in New Zealand. I lose count of the number of different Subaru models we get here at about 100 so i can understand theres plenty of confusion. Its not a Turbo, TX i think was one of the most basic models of Legacy. Its 2000cc, auto, and runs great, just that cheeky little CEL bugger. I flushed the radiator and cleared out dead bugs for africa. doesnt seem to have done much. i’ll see if i can get a code from a subaru service centre.

  115. Hello,

    I have ’96 Subaru Impreza Outback, 2.2L, 122K, recently began making incredible noise and turns out the exhaust system is rusting, specifically the catalytic converter and flanges.

    I am wondering if I might be able to get away with using an after market converter or should I pay more for the Subaru part. I’m hoping to get another year at least out of the car but want expenses kept low. What are your thoughts?

    Thank you!

    1. Hi Rod,

      Thats a tough one. Because the car has so much life left I would steer you towards the Subaru Part. But I do understand the price is going to be really high on a 1996.

      There are some not as legal options such as local classifieds for part outs. But I will leave that up to you.


  116. Or should I just light it on fire and let it burn for insurance money. I’m tired of these problems. I bought it with thought in mind that I’m getting a high quality Japanese car, traded an Olds Aurora, but l think l should of kept it

  117. I have a 2006 outback with 2.5 XT turbo, I’ve had my check engine light coming on for about 2 months. I took it in for an oil change and it started to run like crap. It was kind of running rough before that but now its bad. I replaced the mass air flow sensor & reset the codes by disconnecting the battery, it did’nt fix the problem so I took it to my local subaru dealer, they played with it for 2 hours. They couldn’t find anything that was causing it to run like crap, even driving it plugged into the datascanner, nothinf. Two days later the ce came on, l went back & they said it’s misfiring on cylinder 4, so l switched ignition coils with 2 & 4 and checked it again, now 3 & 4 are misfiring. I put new coils in & the plugs are a year old, and just replaced timing belt, still runs like crap.

    Could this be a knock sensor gone bad? They said at subaru it might be bad gas, gummed up injectors, carbon build up, bad plugs loose gas cap etc. I’m running out of things to replace, kinda. I did replace O2 & fuel mixture sensors 2 months as well. Any ideas on if this could be the knock sensor?

    1. Chris,

      You have a good car with a problem that needs to be accurately diagnosed. Anytime parts are replaced without “knowing it will correct the issue” its a risk and typically an expensive one.

      You need a Subaru Expert, and they don’t work at the Dealer or if they do they weren’t assigned your car that day. Until that happens there will be no resolution.

      There is a diagnostic procedure that is to long and detailed to post. Thats what needs to be done and the solution will be found until then it will continue to be frustrating..

      A Subaru select monitor will show misfire data not just codes, then that data can be broken down further along with tests of the ignition, fuel and mechanical systems including but not limited to injector balance tests, cylinder leakage tests and valve clearance tests. All of these should be done prior to any parts replacement.

      There is a limit to what I can do minus car in front of me, I cant diagnose it from here, and you cant tow it to me, look for a me where you live. I am not the only one who understands how a car functions you just haven’t found that guy yet.


  118. Hi Justin,
    I really appreciate the advice being given in your spare time on this page, now I must ask about my 2002 Outback that is a limited with a manual trans.

    This car has had it’s service engine light on since I bought it 15 months ago with a code of catalyst inefficiency. I had the pair of catalytic converters and the O2 sensors replaced two months ago. The CEL would come back on after driving 40, 60, 80 miles etc… every time I brought it back to the shop. Eventually they had to replace the new parts recently installed and I think they tried to get away with aftermarket stuff, but they put on OEM parts. CEL still comes back on.

    Also had a tune up as well, everything but the spark plugs were changed. They had to have the “computer” in the car reprogrammed and then it went its longest without the light, around 170 miles before it came back on. Last night the CEL started blinking, luckily I was 2 minutes form home and it only did intermittently. It definitely sounded like a misfire to me.

    The car has been in and out of the repair shop 8-9 times and this is still not solved. I trust these guys but beginning to think it might need to go to a dealership, but having $1500 sunk in already I don’t have the cash for that now. At least all these follow up visits have been free haha.

    I think there might be an underlying issue causing the catalytic inefficiency code to come up and now with the misfire, could that possibly be it? I’m really at my wits end with this and now late on getting a state inspection sticker ugh.

    Thanks for any help! Can pull codes tomorrow if needed.
    -Dave in Mass.

    1. Dave,

      First of all you need to invest in a generic code scanner so you have the code number your self each time the light comes on, so we can know if the light is coming on solely for a P0420 or if there are other issues at work.

      Its possible to set a P0420 and not have a failed catalyst which is why testing must be performed, it doesn’t sound on the surface like that has been done, no aftermarket parts will do, they don’t have enough precious metal to be a Catalyst, that’s why they are cheaper.

      Use the search feature of this website and search for the 420 code you will get an idea of the cause of the code.

      Yes you are correct that the check engine light will never blink because of a a P0420 either, only a misfire will cause a flashing check engine light and also damage a catalytic converter regardless of how new it may be.

      Ive never had 8 or 9 opportunities to correct the same code, you are patient. You need to find out what went in the car, what are the results of testing not code scans. A OE catalytic convertor coupled with a cheap generic 02 sensor will cause a check engine light and P0420 code.

      Hope that helps


  119. Hello Justin,
    So relieved to find this blog. Just bought a 2005 Outback 2.5xt today with 71k miles. I have been researching and shopping for a subaru for almost a year, and felt somewhat confident with my purchase. 3 hours later after driving the car 40 miles on the freeway home, I am freaking out, to put it mildly.
    After getting off the freeway, the engine light illuminated and the cruise light flashing. I pulled into my driveway about 4 minutes later to my awaiting family who all started talking about the “burning rubber” smell. I turned off the car, gave it a minute and restarted it. Same lights, and car seems to be idling rougher than I remember it doing so when I left the lot with it. I am so upset about this, but don’t want to overreact. The financing is not done on this deal- would it be a good idea to return the car and not finish the deal?
    Any advice would be so appreciated. I read through 2 years of posts on your blog, and you sound very knowledgeable. Just lost my dad this year who was a master mechanic and helped me with all of this:(

    1. Amy,

      The check engine light can come on for a loose gas cap and this will also cause the cruise light to flash as well (it will every time the check engine is commanded on by the Engine Control Module) I wouldn’t want to give back a good car for a loose gas cap.

      The check engine light can come on for thousands of other reasons as well, based on the information at hand its just not responsible to advise you either way, the burning smell is a concern, but what would have made the most sense was a prepurchase inspection, had that happened you would be comfortable with the car or you wouldn’t have purchased it.

      A plastic bag melted on the exhaust could be the smell, but it could also be a fluid leak which would be a concern.

      It needs to be evaluated locally, and I hate saying this but you have to have any car you are buying inspected before you buy it, or the outcome can be devastating.

      Sorry I cant offer more, and I sincerely hope it turns out ok for you.


  120. Hi Justin,

    I apologize for adding to this giant list of inquiries, but I am hoping you can help me out. I have not yet taken my car to a dealership as you have recommended. I have a 2001 Legacy L, and here are my symptoms:

    CEL Showing code P0328 (knock sensor, chamber 1 or something like that)

    80% of the time my car drives terribly. Slow to accelerate, feels like driving in fifth gear when it should be in first, the other 20% just reminds me how well my car could drive.

    I have replaced knock sensor, changed all fluids, use only premium gas, etc., but the issue persists. After replacing knock sensor, I left the battery unplugged overnight, and CEL stayed off for about 20 miles.

    About a week ago, my CEL turned off while driving and stayed off for a week and a tank and a half of gas.

    Tonight, I filled up at Shell and after about 20 or so miles, the CEL came back on.

    If you have any ideas, I am open to them. Thanks for reading.

    1. Hello Josh,

      The gas level and type have zero to do with the Check engine light, a P0328 could be a faulty Knock Sensor but could also be a wiring or ECM issue as well. The only way to know is to test it, meaning that a DVOM (Digital Volt Ohm Meter) Subaru Select monitor or the equivalent, a factory service publication and someone capable of performing the tests analyzing the data and determining what is wrong.

      I know you are looking for me to tell you something else, but there just isn’t anything else I can responsibly tell you to do. You don’t have to take it the Dealer, but you do need to take it to a Subaru Guy, you have already replaced the knock sensor and that was proven to be noneffective as is the case many times when merely replacing parts based on a code and no diagnoses performed. I didn’t like paying for my MRI , but as I didn’t have any choice I had to as guessing at what was wrong with my shoulder just wasn’t getting the job done. I have to point out that if you want results you are probably at the end of your capabilities.

      There are situations that I just cant help you with without seeing the car first hand and this is one of them.


  121. I need a little help figuring out what to do 1st. My CEL came on yesterday but when Autozone tried to use a codereader on it, there’s no power at the OBD port. I heard the fuse to your cigarette lighter could sometimes blow and would prevent power to the port also but 2 different mechanics (I was harving oil change/tires aligned) couldn’t find the fuse to check if it had blown. What do I need to do to get power to the port so I can figure out what’s causing CEL? Thanks for any help.

      1. That would be why they couldn’t find one, huh? I’m not feeling very confident that there’s anyone around here who understands Subaru’s, and seems as if there’s something unique about their insides that doesn’t correspond with every other car out there (which would be why there great cars, right?). What is likely the problem that would cause no power to the diagnostic port then, everything else in the car seems to be running fine (other than whatever the cause of the CEL coming on is). Should I be taking my car specifically to a Subaru dealership to have repairs done, or should any national chain mechanic shop (Carmax, Firestone, Midas etc.) be able to figure things out? Thanks for being there and all your help on this forum.

        1. Allison,

          I doubt there is a power problem, its most likely that the shops and parts stores near you don’t have a compatible device for your Subaru. I will tell you that anytime there is no communication to a scan tool it typically points to a faulty ECM, this is something only a Subaru guy is competent in diagnosing for you.

          The shops you mentioned have a huge disadvantage over a specialty shop, and the profit model also only allows for cheaper labor costs, cheaper labor costs do not attract the most qualified of Technicians. I started my Career at a Tire store and I have a great understanding of how they operate.

          I don’t like the Subaru dealers unless you can find a smaller market one that works a little harder for your business, I do prefer a Independent Subaru Facility for the best of both worlds.

          What do do from here is try and find a good shop that you can establish a relation ship with, if you can do this your ownership experience will also improve greatly.


  122. Also, I think the day before there seemed to be water on ground….not oil and colorless so not sure related to the issues/Joan

  123. Hi Justin,
    My engine light just went on yesterday but also error message:ER HC 096043, “Sport” and “Cruise” ….. car seems to be running fine but cannot find in manual what these things mean.

    Your website seems to help many people and I hope you have some suggestions for me.

    Joan Reynolds

  124. Good afternoon Justin,

    I have a 1998 Outback. I am currently overseas and will be returning to the US next month. I am being told by the person driving my car while I am here that the check engine light is on and that the code is a vaccum leak. I was wondering if you know someone in the Baltimore, MD area you could recommend you look at it upon my return. Not looking for you diagnose or anything as I have read the site enough to know the CEL is about getting the fault code to start the diagnosis. Was just hoping you might know someone in my area you could recommend to start that process.

    1. Hello Scott,

      Thanks for understanding there is a limit I can offer without a code number and data. I did make a couple of phone calls, and it appears that other than the Dealer there aren’t to many options in that part of the country for you in terms of Independents.

      I would suggest maybe or Google places as places to start searching for a shop in that area.

      Hope that helps


  125. Justin,

    Thanks so much for doing this site on your free time. It’s unusual these days to find such a goldmine of suggestions.

    I have two quick questions, if you’re able to reply. I have a 1996 Brighton, 300k km, and the CEL just popped on, and the only other thing I’ve noticed is the resting idle may be 200-300rpm higher.

    Tried to scan with an ‘Autoguage’ code reader (which works fine on other vehicles tested afterwards), but on the Subaru, would not register a problem code, also wouldn’t clear the CEL light, and finally wouldn’t read the other variables of the car, i.e., the various temperatures, pressures, etc..

    What do you recommend as the next step? Go to my trusted independent mechanic, Subaru dealer, try another code reader? Do you think this could mean the person i purchased it from fiddled with the computer, so as to hide an issue? The car runs like a top otherwise. I’d bring it to you, except I live in a different country!

    Thank you so much for time and thoughts.


    1. I would try another code reader, maybe if there is an autoparts store nearby?

      I will offer however, if the car wont communicate with the scanner, and the check engine light is on, and its idling high, its probably in failsafe mode and may have a faulty ECM (Engine Control Module) this is just a guess but it is a set of symptoms I have seen a few times on the 1996 only.

      I dont suggest running out and buying a new computer, but after some careful evaluation that may be where it takes you.

      Hope that helps, Sorry I dont have better news.


      1. Justin,

        Thanks so much. I had a thought, I read somewhere the scanner should be used with the ignition in the ‘on’ position, but without the engine running, and we had the engine running. Could this be the cause of the failed scan?

        Also, looking at a map, you are only 2hrs away (I live close to the border). If I can’t get things sorted, would it be safe enough to drive there, for your shop to take a look? As I said the vehicle seems to run fine.

        Thanks again, and have a great week!


        1. Most likely it would be ok to drive here, if the check engine light was to start flashing that would be a stop driving it kind of a thing. The scan tool should be able to read codes with the car running.


  126. Just came back from a trip taoday and after stopping my car then restarting it I noticed a lack of power and some rough idling. When I accelerated the CEL started to blink. The CEL was already on and when read recently it indicated I needed a new O2 sensor. I’ve done some research online and have come to the conclussion my engine is misfiring. IM bringing the car to a garage tomorrow to check it out, but was wondering where I’d start in the order of process of elimination. Just would like to fix as cheaply as possible as I’ve recently acquired this car and have sunk about $1000 into it getting it up to par such as brakes and cvs and one wheel bearing.

    1. Hi Shane,

      The process of elimination should be done by the shop doing the diagnoses. A misfire will cause a check engine light to flash, and it should not be driven when the check engine light is flashing. The 02 sensor is most likely not causing the misfire. This is why the code number is important when asking questions. The light is the indication that it needs to be scanned for codes, and then the codes diagnosed per the proper flow chart in order to determine why the code is set.

      Hope that helps


  127. Justin,
    Stumbled upon your site and since I unfortunately have an issue with my wife’s 2007 2.5i I thought I would drop you a line:

    Situation: Car has 74,xxx on it and all maintenance is generally up to date (sans brakes). We recently moved down to Georgia from the northeast and during the last 3 hours of the trip the check engine light came on and the cruise light began to flash. The car felt as if it lost a cylinder (this is relayed from my wife as she drove the car herself). The light then went off by itself.

    A couple days later we had the car taken to a local shop just to have a check done and ensure things were OK. They found nothing wrong. About a week later the problem returned as the car was idling very rough and the CEL returned. We brought it back to the shop and they initially thought it was a misfire due to a bad coil. After replacing the coil they were still left with the misfire. At that point they ran a compression test and attempted to run a leakdown test a few times. They also swapped the spark plugs to see if that was the issue. Essentially at this point nothing in the realm of igition issues seems to be causing the misfire and they are convinced that the cylinder 4 misfire is either due to a burnt exhaust valve and / or lifter isse.

    They have quoted me $1,5xx plus machine shop fees for grinding the new valve. My question is given the mileage is this something that is even remotely common (i.e. burnt value causing a misfire issue?). This is my 3rd Subaru (I had a 2003 WRX and currently drive an 09 WRX) and this is the first real issue I have had to deal with. I am really disappointed that a car with 74,xxx may need to have a new valve at this stage of its life…

    If you have any thoughts I would appreciate it…

    1. HI Josh,

      Its not common for a 2007 to develop a burnt valve. That doesn’t mean it cant happen.

      No shop in the world should struggle with a misfire diagnoses if its acting up when they view it.

      A burnt valve will create low compression and at least 20% leakage to the exhaust, it doesn’t have a choice its a mechanical fact. It should not be hard to spot with low compression and leakage, thats the part based on your post I dont quite understand.

      Now if its a matter of who is paying for what kind of tests that’s different.

      At 1500.00 I fear the job is being quoted incompletely? It should be both sides, and you should plan on replacing your timing components while it is apart. May be the labor prices where the car is is a whole lot cheaper than where I live?

      Without seeing it for my self I really cant confirm the diagnoses, typically for a exhaust valve to burn that early it was overheated as per lack of lubrication or there is a exhaust leak close to the valve somewhere.

      Hope that helps


  128. Hey there,
    2005 forester 175k miles. CEL light comes on with the cylinder 3 misfire. replaced plugs, wires and coil. I know there is a leak with the head gaskets and working on the funds to fix that one. But not sure if that is causing the misfire or if it is something else. It runs just fine, but on occasion on start-up it idles a little shaky. after 3-4 normal starts, the light resets itself, only to turn back on in the next 1-3 start-ups. Suggestions here? All the techs are baffled whether or not the head gasket is causing this or if something bigger.

    1. Have the “techs” look at the Valve guides.

      Use the search feature on our website and you will find an article with a Video.

      There is no reason any Tech should be baffled with a Misfire. The internal combustion engine while it has gone though changes still uses the same basic principles for proper combustion.

      Were the plugs, wires and coil found to be faulty or was that a guess?


      1. it was more of a guess since they were cheap and the wires hadn’t ever been replaced. the plugs had been so we were more iffy on replacing them again. we borrowed a coil to test that before making that purchase and it still does the same thing. I’ll talk to them about your suggestion as well. I’m shooting for the cheapest fix so I can sell it. I’ve got a new 2012 outback on order.

  129. Great site sir,

    Had a 86 justy in the Navy in the 80’s loved it…had Toy’s my entire adult life…02 Tundra with 123 K on her…but gas is killing…so I went back and searched for a Forester because I wanted AWD and 4 cyl on a good car…found one wholesale…took it home…CEL comes on..took it to Auto Zone…air intake code came up…dont have it in front of me to tell you exactly… But I see that others have had this problem so I went and purchased CRC MAF cleaner and started cleaning components…and the entire air intake system…car was running fantastic..quick…no hesitation…after that cleaning this morning it will go and then sputter…and rev high to about 3000 rpms and chirp and the AT Oil light came on…it has a K & N filter…Now I thought it had a MAF but another person told me it might not so what did I Clean…they asked for pics of it..unfortunetly I work midnights…so I will have to take them tomorrow….I am very upset becuase I love that car already and it was riding great even with the CEL on… I will tell you I unscrewed what I thought was the MAF and sprayed the CRC on the component and put it back together… I hope I didnt screw it up…thanks. RJ

  130. Hey Justin, I have a 98 impreza 2.2L and my CEL just came on today. It was cold this morning so I started my car to warm it for 5-10 mins then drove to work (5min ride). When I was parking the car felt like it was going to stall, but it didn’t. Fast Forward: leaving work I started my car but it stalled a few seconds after it started. I started the car again and slightly gave it gas when it felt like it was going to stall again. I held the engine at about 1000-1500 for 20 seconds or so and the engine seemed fine but I looked and saw the CEL was on. I drove home and did a visual check of the engine bay and saw nothing obvious. I did hear the air intake sound like it was working pretty hard so I shut the car off and checked the filter and it was very clean. I restarted the car and it was still weak sounding and when I held the engine at 2500 rpm the sound was not smooth it faltered as I held the gas.

    When I purchased the car used I had the plugs and wires replaced, fresh oil change/filter, fuel system cleaner, oil restore treatment, new air filter, brakes replaced (rotors, pads, drums). I have maybe put 1,000 miles on it in the past year.

    Any ideas?

    I’m going to try and have it hooked up to an OBD II scanner this weekend to try and diagnose a little better but any help would be appreciated.

    1. When you get the code number I may be able to provide some insight but there is not much I can say without the code number and then really its possible that it wont be enough to offer much help either.

      Sometimes data from sensors is also needed to offer much in the way of help. Generic OBD scan tools dont always offer this.


  131. Justin,
    I have very little knowledge on cars so please bear with me… About a month ago, my fiancé attempted to start our car (1995 Legacy wagon) shortly after turning it off. It sounded like it was going to start but never actually turned over. He tried this quite a few times until the cat’s attempt at starting no longer happened and all he got was a “click.” We had a local mechanic check it out and they replaced the starter. It worked fine after that for about a week. Then it would occasionally stall while idling. (did this about 5 times over a period of about 2 weeks) we had it checked by another mechanic because the CEL was flashing when we received it back from the first one. Turns out they had forgotten to unplug the diagnostics cord. The second mechanic said there was nothing wrong with the car. Three times in the last two weeks (after getting it back from the second mechanic) it refuses to start just like it had in the beginning. It sounds like it’s going to but doesn’t actually turn over. We usually sit and stress about it, weighing our options, for about 5-10 minutes and then try it again. Eventually it does start for us (so far) but the CEL comes on after it starts. We intend to get the codes read on it but every time we have the opportunity to take it to autozone the CEL has turned itself off. Any suggestions or ideas would be very much appreciated.
    Thank you!

    1. Hi Mary,

      Sounds like this has been Quite a ride!

      The code will stay in memory even if the light goes out for a period of time depending on what system is affected, so it may still be wise to run it by Autozone the next time the light comes on even if the light goes off the next day, I do have to point out that Auto zone can give you codes and may guess right, but cannot actually diagnose the car. The “click” no start and the Check engine light don’t have anything to do with another.

      Really it just needs to find its way to a good Subaru tech, or it will be more of the same I am afraid. It could be that the starter is defective, the ignition switch worn, it could have a faulty sensor causing the intermittent check engine light as well.

      I dont understand what diagnostic cord would have been left plugged in unless he was referring to the D check connector, which by the way there would have been no reason to connect to diagnose a “click no start”

      As far as the staling that’s also probably not related to the starting issue either.

      I know that it all probably seemed like it was fine until the first no start and that it should of only needed one thing to correct it, but sometimes multiple issues can crop up during similar time frames.

      IO wish I could solidly point you in any one direction but its just not possible with out seeing the car first hand or having some data such as a code number or ISC percentage.

      Sorry I cant offer more


  132. Justin,
    What if there is no CEL that comes on and you get in your car one day and it wont start? This past monday morning I got in my 05 Legacy GT w/ 79,000 miles. When I turned the key it acted as if the starter engaged for a second then disengaged and made the typical motor winding sound. I tried it several more times with the same result. So I reluctantly called my local repair shop and had it hauled over for what I thought was possibly a bad starter. The mechanic went out to check it to see what it was doing and when he did, it started right up… WTH!!! He said that when it started it ran as if it had been flooded for a minute or two then cleared up. Throughout the day he drove it around and started it about 20 times and said it “appears” to be ok. I’m guessing your going to ask me if he pulled a code on it…the answer is no. It’s a small shop that I trust with my other cars but they don’t have the tech to pull codes on a subaru. So my question to you is, in your experience have you seen anything like this and do you recommend I get my car into my subaru dealer (who is an hour away) and have it checked out properly?

    1. Hello Louis,

      Its very possible it was just flooded? And the Computer has now way of detecting this so it cant report the issue VIA a check engine light. I will tell you that this comes up at the beginning of every Fall and winter however.

      Here is why.

      The worst thing you can do with a horizontally opposed engine is start it up , let it run for a few moments say to move it out of the wife’s way or run back into the house after something you forgot. May times when you try to restart it, either moments later or the next day that engine may in fact be flooded as there was just to much fuel that entered the combustion chamber and was not burnt.

      When the temperatures come down this issue is made much more pronounced as the computer feeds a cold engine much more fuel.

      On an inline engine or a V design the excess fuel will literally pool on top of the pistons and will slowly evaporate. But on a H engine the fuel actual collects on the cylinder walls, which will diminish the ability of the engine to build compression as the friction needed by the piston rings making contact with the cylinder walls. With out compression there is no explosion all while the computer is adding more fuel to the “no fire”.

      The right thing to do is to floor the gas pedal while trying to start a flooded engine as it will do two things one is increase the air coming in, and second is to put the engine into “clear flood mode” by shutting off the injectors.

      I dont know if this at all fits your scenario, I also would have suggested the Tech pull codes as most likely there wouldn’t be any unless your check engine light doesn’t come on because someone removed the bulb?

      Dont see a lot of no starts on the GT models that aren’t related to low or no fuel pressure, I would suggest that maybe a fuel pressure test should be performed if it wasn’t just a flooded situation based on what I tried to lay out earlier.

      Hope that helps


  133. my 05 sti is giving me serious grief. When I accelerate up to speed, it feels pretty much normal. When Im cruising (no matter what gear it is) it FEELS like the brakes come on. Or cuts power for a second. Im sitting there and body rocking every 2-3 secs. Its frustrating, annoying, and basically inoperable

    It went in for a timing belt change (99k) on tuesday. The dealer ran the “check engine” and it came up an 02 sensor. They cleaned it, but its not fixed. I trust them totally, but im thinking maybe its combined with something else. Ive had an 02 sensor go out on a WRX and it wasnt noticeable.

    Its turning into a money dump. Clutch two months ago $1500, timing belt $614, the sensor about 100-300$

    The turbo pegs at .1 or whatever. the gauge goes to .15 I believe. bad turbo? It drinks oil, and when I checked coolant, I noticed it was low…this all started happening when I bought another car for daily driving. Needy car. Any input would be appreciated.

    1. Yes an STI is a very needy car, its a Performance vehicle, and I have never come across one that didn’t get into your wallet. I am sorry if you were previously unaware of this, but you can expect to put $$ in a performance car and on a STI right at about the 100k mark.

      I cant offer you any real advice on your Symptoms with the amount of information you have provided me, if it was diagnosed with a failed 02 sensor and merely cleaned as an attempt to repair that may be the best place to start.

      The STI is typically reliable but at the mileage it has its ready for a round of service and repairs to maintain that reliability.


  134. Hello Justin,
    This morning when I started my 2001 Subaru Forester S it ideled rough – like one or two cylinders were not firing. CEL came on flashing. I checked the oil and at first it was a little low but second check showed normal level. I did notice tini bubles in the oil. Also the coolent level is low. I pulled two of the spark plug wires and notices a little bit of oil around the rubber. Don’t have engine codes yet. Any ideas what might be going on? Car has just over 101,000 miles on and up to this point was working great.
    Please help.
    Thank you in advance for your time Justin! Really appreciate any advice you can give.

    1. The flashing check engine light indicates a cylinder misfire and the Subaru needs to be repaired ASAP and not driven until it is repaired, you need some basic tools such as a code reader to know which cylinder is acting up by using the codes set as a starting point in your Diagnoses. A common thing would be oil soaked plug wires causing cylinder misfires you could do at least a visual inspection, but the repair would be to replace the plugs, wires, and reseal the spark plug tube seals and valve cover gaskets. If the plug wires are not oil soaked you would need to look else where.

      You will than need to diagnose whats wrong, this can be as simple as a faulty spark plug or spark plug wire or as expensive as a bad valve. Not everyone is up to the task or diagnosing and repairing this situation, and if not you would be best served to seek out some help local to you. With out the code number I have no where to send you to start out with, if you buy plugs and wires and it doesn’t change anything you have us spent money that you didnt need to.

      Hope that helps


  135. Justin… Hello and HELP!!!!
    Daughter has a 1999 Sub Legacy that has been a nightmare lately.
    By her own fault and some bad mechanics advise she has had to replace the tranny, rebuild the engine/ rebore heads, and recently again rebuild the tranny. On top of that almost everything under the hood has been replaced over the last 2 years. But……
    we keep getting a CEL going off.. the codes read Knoc sensor which was replaced. Then a week later it again went off again reading knoc sensor but this time they found a partially cut through spark plug and so replaced all that. Now a month later, CEL went off again, this time the Pep boys techs say its the catalytic converter ( not sure if they got a P0420 orP0430 code).. Car has been running like a dream – no hesitations, idles ok, good gas milage
    from reading some of the above posts.. I pretty well doubt they did more than just code read and looking at a $5-900+ job again for this car based on just a code # doesn’t seem to make sense from what I’m reading.
    She can’t afford another big repair like that nor to replace the car yet. The Techs told her its ok to just keep driving the car until next June when her inspection is due….. since this kind of mechanics advise from other folks is why we have replaced 2 trannys and an engine.. I’m a bit skeptical at this point.
    Any ideas or suggestions?

    1. If it setting a po420 than most likely it needs a catalytic convertor replacement.

      Based on what she has had o put into the car , I would invest in a code scanner for here to learn how to use( which is very simple) and put off the repair until absolutely needed. The light will continue to come on, but this way she can read the code herself to make sure its not something new occurring as there is only one light and hundreds of fault codes and even more possibilities of why.

      Here is a link to one that I like

      I do sympathize with the amount she has had to lay out in repair costs and thin that based on the code you are telling me about its ok to ignore for now, but I do strongly suggest backing that up with a code reader to leave in the glove box and scan it herself to ensure she is never stranded.

      Hope that helps


      1. Thanks Justin.. that’s one of the suggestions I gave her.. if she chose to run the car just keep checking the codes to make sure it wasn’t something else going bad.
        Funny thing.. yesterday the light turned itself off and hasn’t gone back on…??? Not sure why or what.. could it be maybe a plug? She has a tendency to run the tank down to a whisper of gas and I have been wacking her upside the head about NOT doing this due to junk in the bottom of the tank ( or is that an old wives tale?)
        Before we replace the converter ( if this light comes back on with the same code) I have told her it sounds like it might be a good idea to drive to your shop for a second opinion!
        Thanks so much for the above advise and any other ideas you can give.. so glad I found this site and appreciate what your doing to help folks like us!

  136. Hi Justin,

    Thanks so much for offering this very informative forum. I have an 2008 Outback Sport with <20K miles.

    This past weekend I was on a highway following a slower driver. The cruise control was "on" but not engaged. We were going approximately 60 mph. I pulled into the oncoming traffic lane to pass, and upon stepping vigorously on the accelerator, the car lost a lot of power and was unable to accelerate at all. The traction control light came ON suddenly (meaning TCS was now off). And the CEL started to flash. I do not believe the cruise control light did anything unusual. I pulled back into my original lane, pressed the traction control button to re-engage it, and the flashing check engine light disappeared.

    Any idea what could have happened? The car has driven normally since that episode (the only time) with no unusual warning lights.

      1. Thanks so much for your expertise. Do you have any more specific info regarding the logic reflash I can provide the local dealer? I just spoke with them over the phone here in Portland and they were a bit baffled. Since the warning lights are off and things are running normally, they said it would be hard to pinpoint things. I did have the most recent ECM recall reprogram issued to a lot of different models this past Spring.

        I may try to reproduce the situation, only not into oncoming traffic this time =).

        1. Hi Wayne,

          There is a TSB floating around about the issue its a year or two old so its probably not fresh in their mind.

          That’s also the game they play, even if I give you the Pack number they still want to charge you to look at it.


  137. Hello,

    I have an ’02 Legacy B4 Twin turbo bought in Japan(84,000 km or 52,200 miles) that has been acting crazy, something never experienced with any other vehicle. In the past, it had trouble starting in the winter and the dealer replaced the fuel filter which seemed to fix the starting problem, however it had this weird shaking side to side (barely noticeable at first) initially and then it would subside. Its been 4 months since the fuel filter was replaced but now the shaking is more prominent at startup and when you try to drive with the a/c on, it shakes violently and if you try to accelerate, the transmission light/ check engine light blinks (never stays lit) and it feels like its about to stall, however when you shut the a/c off it drives fine. I’ve also noticed the rpms at idle are about 150 to 200. I spoke to this one guy and he thinks it maybe the idle control module that needs replacing which could run about $1000. He said others have had this problem with their legacys too. Not sure if this has anything to do with my current problem but I also want to mention, in the past there was a fuel line leak up front which was found and fixed. Any help or info would be most appreciated.


  138. Hi Justin,

    I’ve owned my 01 Subaru Forester GT for about 6 hours, and now it won’t drive. The check engine lamp is on, and the car starts but it won’t let me get the revs up. It’s like it’s in some sort of ‘limp home in on idle revs’ mode.

    I’ve got to take it to a dealership here in Australia, but would like to have a better general idea of a possible cause.

    I thought I heard the sound of a hose releasing air while driving it earlier but couldn’t see anything obvious when i looked under the hood.

    any thoughts?


    1. Hi Andrew,

      There isnt anything I can offer you from here. Without first hand knowledge of the exact symptoms plus a visual , audible inspection under the hood plus some data from sensors its all just a guess.


  139. Justin,

    I have a 2007 Forester with 65k miles. The solid check engine light with blinking cruise light. I had the gas cap replaced and reset the system. Lights came back on. Dealer says its a fuel tank roll over valve. About $500 to replace($90 part-4hr labor). Any suggestions? thank you

    1. My suggestion is to fix it.

      You should also ALWAYS know the code number set when the check engine light comes on, that way if the light comes back on later and its the same code number you know there is still a problem with the same system. If the light comes back on with the different code than its a different system this time that needs to be evaluated.


      1. Sometimes I wonder about all the computer monitoring that goes on in modern cars. If you put a space shuttle type monitoring system in a car it would run a lot more eco friendly. Is there a point that we have too much monitoring.

        I’m currently running down an intermittent code 400 on my son’s new-to-him 95 Legacy wagon car. It runs well, gas mileage is great and would rather the code be a component code.

        The car lot that sold the car put a replacement 2.2 engine in the car and I am suspecting a possible electrical condition. Although that EGR valve was caked with carbon unlike any I have ever seen. IMHO some of the vac ports are way too small and are apt to get clogged with carbon. All of which cost people that know nothing of cars, far too much money.

        I am really enjoying working on the Subbie because of its simplicity. Compared to my over engineered Jag the Subbie is wonderful to work on. But I do wonder about putting all those sensors, etc. under the intake. The engineers must have had small hands. 🙂

        1. We achieved above Space shuttle status in the mid 90’s when GM came out with the P6 processor.

          The average driver has no idea how complicated a 2011 vehicle has now become.

          We are at very low levels of emissions with multiple emissions systems and monitors for each of them to get there.

          “But I do wonder about putting all those sensors, etc. under the intake. The engineers must have had small hands. ”

          Those components were put on the intake before it was installed on the engine and before the engine was installed in your Subaru.

          P0400, start with testing the transducer for the EGR.


          1. Yes I know they were installed before installing the intake, I was really referencing those future owners/shop people who must get at them.

            The transducer was my first check because apparently they are the first culprit and it tested well.

            One thing I have yet to replace is the EGR valve gasket. After cleaning out all the EGR gunk, cleaning the throttle body, installing new vac lines, etc. I didn’t have a gasket on hand. I now have one in hand but want to be sure that I won’t again need to remove the EGR valve before installing it.

            I’ve been thinking about getting a smoke test but I’m not yet to that point. SOmetimes the problem is staring you in the face…ya just don’t see it. I remember one time I changed engines on one of my Jags. Buttoned everything up but it wouldn’t start. Two weeks later and by luck I saw the bundle of ground wires on an eyelet that had been stuffed down when I dropped in the engine. I immediately knew what they were and were they were to be attached. Attached them and the engine fired up. They were the ground bundle for the injectors.

            So I am in the looking stage of the P400 code.

  140. hi all

    well I had my CEL on last week and brought the Subaru legacy GT to a Subaru certified mechanics here in Montreal quebec. I bought the car in California, and the 4 years I lived there she has never experienced the canadian winter. She did great for the 3 first years here in quebec until the CEL lights on. I have 160K miles on it.
    As the major tune up was due I did that and they replaced spark plugs, cover gasket seal, all the fluids and coolant, filter…. But still the CEL was on. so they went into a sorrow inspection and after replacing fuel injector in cylinder 1 (only 3 cylinders were working), a wire, knock sensor; the car does not have the CEL anymore.
    I had code P0325, and i guess two other ones for the wire and the injector.
    My point is that the certified mechanic did a good job, and the car is driving like new or almost as it is 11 years old. I has a cost though as I spent 2000 dollars. THe major tune up cost $1000 alone. It is the first time the car gives me major trouble, but I hope she’ll be driving for 100K more ti finally go to Subaru heaven.

  141. Very helpful site. Justin is most effective when he answers the questions directly without preaching the need for professional diagnostics. People would not be here were they not in need of a professional opinion. Still you deserve kudos; I would take my scooby to your shop. Keep up the good work.

    1. The problem is that each situation is different and some instances require expertise. That is why some can be answered and some need help, also I try to get a sense for the skill set of the questioner, and not everyone is cut out to make their own repairs. This starts with listing codes that don’t exist for their model and continues on with a real lack of understanding about OBDII. When I get posts about someone not wanting to get burned, I understand that and do want to help, but there are just as many who just don’t want to pay to have a diagnoses done.

      Some codes are easy and straight forward, others Require Data to diagnose, the data is typically only available by graphing with a Subaru Select monitor and laptop or equivalent.

      When you go to a Doctor, sometimes he or she has to defer to tests to make a diagnoses, the same rings true for your car in some cases.

      We live in a world where a check engine light comes one time as a loose gas cap, and another time minutes before the car leaves you stranded, the information to the driver is the same.

      I have a doctor that I call and make an appointment o see when I am above my ability to figure out what is wrong with me, anyone who ones a car or a house or a dog that doesn’t practice the exact same principle is bound to be frustrated.

      Those that want to do a lot of their own repairs have that right, and we have many customers that only come to us when they are above their Scope or Skill set.

      I try to help everyone, but at the same time cant and wont completely devalue my profession as a whole to help a few. Sometimes the best advice I have is to establish a relationship with a good service provider they exist in every state the Market place demands it and use them when you need to for some that’s every instance and for others its just once and awhile.


  142. Justin, I am basically at wits end with my 02 Legacy gt, 2.5l. The car is a 5 speed manual, when I put it into first, and go to accelerate the car will bronk and buck violently then at a higher rpm in first will finally accel to about 3k then I shift, into second and the engine idle is really rough. It seems as if when cruising at 30-40mph and I go to give gas, it seems like the engine goes to an on or off switch meaning there is no in between acceleration..While stationary if I rev the rpm, it will dip so low then sometimes stall..I believe I had the p0305 which was the IACV..I replaced that, ran great for a week or so, then it is back to bronking and bucking. I ran seafoam, injector cleaner, still no fix. The IACV is not dirty whatsoever..I am also not getting any other codes…the cat was replaced as well as new o2 sensors..does this sound like an EGR. MAP, TPS issue? Thanks for your help!

    1. P0 305 is cylinder # 5 misfire, which doesn’t exist on a 4 cylinder Outback.


      Sometimes you can take care of an issue your self and sometimes you need a pro on your side, it sounds like the latter is where you are at.

      I can send you on half a dozen wild goose chases and you can spend money on parts, but what you really need is to have someone local to you do a real diagnoses, not a code scan not a guess but evaluate the systems and figure out whats wrong. It does cost money but what other real choice do you have?


  143. hi !
    mine is a Subaru outback impreza sport 1998;
    when I plug the OBD II, it reads as follows:
    fault: 2; pending : 0
    fault 1 : PO 325 book : (knock sensor 1 circuit malfunction bank 1 or 1 sensor)
    fault 2 : PO 440 : book : Evap emission control system malfunction

    my question : is it serious ? or I can carry on like this ?? I may think it is only a problem of polution (PO 440) or could it be possible that the Subaru is more thirsty ?? (because of this malfunction) a friend suggest that I should put Super gas to resolve the PO 325, as I am just filling the car with regular unleaded right now; what do you think ?

    thanks a lot !


    1. Super gas wont resolve a failed knock sensor.

      Most likely it has a failed knock sensor, very common but the circuit should be tested to verify this. Possible ramifications are overall longevity of the engine and reduced fuel economy if not repaired.

      To the P0440 either the Gas cap is faulty, the system has a Evap leak or there is an electrical issue.

      Hope that helps

  144. Hi Justin, I have a 2000 Subaru Outback. Had the car for about 6 mo. I did the timing belt, water pump, front 02 sensor, new alternator,battery, PCV valve, air filter, cleaned MAP and IAC valve. I haven’t replaced plugs and wires yet because they looked okay. The car is throwing a 0420 signal and a 0107. Cat system and MAP sensor respectively. It will idle low at times after warmed up to the point of vibrating around 500 RPM. It will stay low but has only actually died a few times. The 0107 goes off usually when the car is decelrating from Hwy speeds and shudder and dies sometimes but not always. Then the CEL will come on and AT light will flash but resets. What’s my next move? Other than a shady authorized dealer here in SW Mo. I don’t really know who to go to for a good Cat test. And the MAP sensor thing is just confusing. I understand what it does but so far nothing is working. Should I go ahead and replace the plugs and wires as well, maybe the fuel filter? Any help would be appreciated!

    1. The map code is most likely a result of the low idle not the other way around, the Catalyst code is most likely a failed Cat.

      With out data there isnt much I can offer, if its a 5 speed it could have a failed “n” switch but there are so many other possibilities I hate for you to get into a parts toss.


      1. Sorry it is an automatic. Is a back pressure check a good enough Cat test? I don’t trust the Subaru dealer here at all. It is a large multi-car dealership that is famous for being dishonest. And no Subie specialized indy shops. I will probably have to rely on them. Any advice on what I should look for, or have them check when I take it in for a good overall scan. I’m not even sure which shops would have the software to do it correctly. I’m afraid of getting screwed because someone doesn’t know Subarus.

        1. Back Pressure does not correlate to function only confirms restriction.

          There are a few different Catalyst tests that can be done but all require the proper test equipment and the skills to use them.

          The most common method is graphing data with the select monitor you can read about it here.

          I am sorry that I cant help more, but there has to be a good shop somewhere near you?


  145. i bought a Subaru B4 Twin Turbo legacy 1998 model.Recently it started to loose power and gains the power while im driving as if im running low on gas.And also whilst im driving it shakes as if the gas is closing.What might be the problem.i thot it was fuel pump and i replaced it and keeps doing the same.The engine check light is on after replacing the fuel pump.

  146. Hi Justin,
    excellent website, first of all.
    I purchased my 2005 Subaru Impreza RS two years ago with 42,000 miles. now i am up to 73,000 miles. when i got the car it had this very slight chatter when accelerating or climbing hills, or maintaining speeds on the highway. Until very recently i thought this noise was some sort of bearing, but now i understand that it is spark knock. i searched some videos of cars with spark knock to compare the sound, and that is definately it. now my spark knock is extremely noticeable once i’ve been driving for a little bit. the noise is especially pronounced on the highway, climbing grades. i will get the noise at slow speeds climbing hills as well. i can control the knock level easily, and sometimes the noise changes from a chatter into a much harder chatter(at which point i would turn cruise control off or reduce/increase throttle) i’m currently at college, but once i go home again i will replace the knock sensor pronto. i have continuously used marvel mystery oil as a fuel cleaner, with great results. i replaced the plugs recently as well. my question is: why isnt my check engine light on? there is a clear spark knock, and i have maintained it very well, and used a fuel additive in the proper amount, continuously. i also have a scangauge2 hooked up to the car, i plan on watching my ignition advance readings while the knock occurs, as well as watching the readings while i tap next to the sensor with a screwdriver. Is it possible for the sensor to go bad, with no CEL?

    Thanks so much,

    1. You wouldn’t have a failed knock sensor on a 2005 model.

      Without a Subaru Select monitor graphing data there will be no diagnoses only guess work. There is a limit to what you can test with out one.

      As far as no light, its one of those situations where the amount of knocking correction is not triggering a fault code. The possibilities as to why are numerous most likely the ECM is defective, that doesn’t mean rush out and buy one just that it needs to be evaluated.


  147. Hi Justin,

    Here’s my code: 0325 (misfire cylinder 1) on 1997 outback

    Had the head gasket replaced twice a couple years back… first time not sure but second time RHS only (not side with cylinder 1). check engine came on about a year back, and I just assumed it was head gasket again since outbacks 1996-99 are known for that.

    Last weekend I checked the wires by swapping cyl 1 and 3 wires – still got 0325. Replaced the spark plug on cylinder one – the old one: although the tip was dry, the gap had gone way up to .0053″ (maybe missing a zero there).

    Initial results were good, check engine was off when I started the engine and on subsequent short (6 mile) trip including a stop at autozone half way through.

    next morning, the CEL was back. I reset it while I’m driving with my code checker and notice that it tends to turn on right after experiencing hesitation (likely due to misfire) in acceleration, which usually happens if i accelerate quickly or on a grade. I smell faint burning oil (what I’d call normal for a 14 year old car) when I park (likely slight oil leak) – it’s not detectable while driving. Note the coolant temp is rock solid in the middle, no variation when misfires occur.

    2 questions – does this sound like the head gasket again? does the increased gap mean anything other than an old plug? (it was fairly low end, and about 1.5-2 years old).
    Second is there a way to disable the knock sensor so I can pass my smog check? 🙂 Last time my measurements were all way below limits, but CEL on forced a retest and cost of replacing the EGR valve)

    1. Well Jeff,

      PO325 is not a Misfire Code, I would stop using whatever code scanner you have and buy a better one.

      PO325 pertains to the possibility of a failed knock sensor, problem with the circuit or ECM.


  148. Justin,

    Thank you for all the great advice!

    Not sure you can do much for me as I don’t have the code but I’ll explain anyway…

    About a month ago, after returning from a four hour drive, I noticed smoke coming from the front of the engine. Took my 2005 Outback 2.5 to the dealer (as it’s still under the extended warranty – 83k miles) and they found that the CRV boots if the front were cracked and throwing grease onto the manifold which was causing the smoke and burning smell. After having them replaced, a tune-up and oil change, I thought everything was fine. Then last night, one month later, the check engine light and flashing cruise came on.

    I’m taking it back to the dealer tomorrow to have it checked but was wondering if there’s any connection between the grease being thrown on the manifold and the light now coming on? Sorry I don’t have a code for you to work with.

    Thanks for any help!


    1. Hi Dan,

      They wont be related. And yes with out a code there is no direction.

      The check engine light comes on only when the Computer sees a problem with a sensor, control device or the presence or lack there of of a system monitoring device indicating a system that is no longer functioning properly.

      I am not sure what kind of Tune up you had There aren’t any specified by Subaru other than the 30/60/90k services but there again there is nothing to “tune”, its just an archaic term that I try to point out that shouldn’t be used with modern vehicles and really only adds to the confusion about what type of services you might be paying for..

      The check engine light is also mostly about the vehicles emissions system and not about the engine, look to your federal government for this inefficiency.

      You can also read about the light and its causes in the Owners manual

      Hope that helps


      1. Justin,

        Thanks for the info.

        It was in fact the 60K SERVICE that was performed, not a tune-up!

        In looking through my paperwork, I found a Service Program WVH-18, Engine Control Module Reprogamming letter for cars registered in CA, MA, ME, NY or VT, which was sent to me from Subaru in June 2009. The letter states that under certain driving patterns the catalytic converts may devolp high internal temperatures that ‘exceed the design parameters. This condition may eventually degrade the effciency of the converters (The check engine light will illuminate to alert you if the converter efficiency has degraded beyond an acceptable level…”
        I took the car in and had the reprogramming done in July 2009, but I’m just wondering if this may be related in some way?
        Just thinking out loud (since without a code there’s not much more I do!) and throwing this info out there. Since you’re located in WA, not sure if you knew about this or not.

        Thanks again!


        1. Hi Dan,

          The check engine light can come on for a loose gas cap, a failed catalytic converter , a defective sensor and a thousand other reasons.

          The light coming on now wont be related to the reflash that took place in 2009, its possible that another reflash is needed for something else, but its also possible there is just something new that came up. The electrical items in your car work in the same fashion a light bulb does and are subject to the same rules of failure. If control device or solenoid has failed to function or an 02 sensor is no longer as active in sampling rates as it was when its was new the check engine light will come on.

          It sounds like not knowing is bothering you a bit. I suggest you look into purchasing a basic can bus compatible code scanner so that when and if the light comes on you can at least scan for codes.

          Here is a link to one that I happen to like


          1. Thank you, Justin!

            You can tell that the not knowing IS bothering me. I’ll invest in a code reader and let you know what I find out from the dealer tomorrow. I’m praying to the Extended Warranty Gods that whatever it is will be covered!

            Thank you again for all the helpful advice!


          2. Justin,

            Just wanted to give you an update on my check engine light…

            Just heard back from the dealer that both catalytic converters went out. Thankfully when he called, it was to tell me that the car was ready and that these were one of the few parts that was covered under the extended warranty so they went ahead and replaced them. Big sigh and thanks to you (for all the advice) and to the Extended Warranty Gods (who are still watching over me!)


  149. I have a 2005 Outback LL Bean, H6 engine, 40,500 on the odo. I have had a recurring problem with a burning or hot ‘rubber’ smell, that will occur when the car is on a long up hill grade. Usually the car has to downshift to keep the RPM’s up. I have had the O2 sensors replaced, and the cats replaced (at different visits). The O2 sensors broke when the Subie mechanics were trying to remove them. I know the cats get hot, but the dealer can’t seem to explain what the bad smell is from. After several months, the smell is back and I think the dealer is going to give me the run around. In addition, the check engine light is on and I have to get that looked at. The CEL was on a couple of weeks ago, but I think it was related to the gas cap. It finally cleared, but, now 2 weeks later it has returned and I have not touched the gas cap. Something else must be wrong. Any suggestions?

      1. I got a P0442 code (per dealer) O2 sensor failure. They tested it and said it was within spec and cleared the code and gave me the CA smog cert that was due. It was suggested that if the problem returns, then I should replace the O2 sensor for about $350. Aren’t the O2 sensors under the emissions warranty? I am worried that they might break it trying to get it out (that happened once before) and I’d have to pay much more for the extra parts.

        1. PO 442 is Evap emissions (small leak), there isn’t an O2 sensor in the world that will fix that code.

          Not knowing model, year or mileage its tough to say if there is a warranty issue.

          The 02 sensors are also covered under the 3 year 36k warranty only unless you bought a extended warranty. All of this and what is covered by the Federal emissions warranty is in fact covered in your owners manual.


          1. The car is an 05 OB LLB edition, H6, 42,200 on the odo. Cats and O2 sensors replaced previously (13K). The dealer invoice states, “Oxygen sensor failure. Tested Oxygen sensor (s). Working properly. Cleared control unit. System working properly at this time” Your comments seem very different from what I have been told by the dealer. Do I need a new mechanic? Do you make house calls?

          2. Either you have read it wrong or they made a typo in the code number. P0442 is related to the Evaporative emissions system.

            O2 codes would be P132 133 134, 135 etc its a federal law all manufactures have to adhere to the P0400 series is Auxiliary Emissions type systems.

            Google OBDII codes and research it your self.

  150. My 17 year old just bought what we will call a beater car….a 1994 station wagon. Engine was replaced with a 175,000 mile engine. The CEL came on at the lot, code was misfire in cylinder 3. Cleared the code and we took it for a drive. No code came on. This car will be driven about 10 miles a day and for $1,000 not much can be expected of it. Drove the car home and sometime during the 30 minute trip the CEL came on again. I don’t have a code reader but would guess it is the #3 cylinder.

    He just brought it home tonight and haven’t done any tune up things like wires, etc. For his sake I’m hoping it just needs a new set of plug wires, that #3 is arching.

    I’m lucky. My car has a built-in code reader. If a CEL is thrown, I can press the VCM and get the code, look up the code and fix it.

  151. Hello,

    I have a 2010 Subaru Forrester. Today the check engine light appeard along with the cruise light which continues to flash. Please advise.

  152. Wow! I have been a Subaru owner for 17 years, and this is the first time I have come across this site! What a great resource! Thanks in advance for your time!

    I have an ’05 Outback with 87,000 miles on it that was showing a CEL (& cruise flashing). I took it to the local Subaru dealership, where they ran diagnostics and found nothing to be wrong, so they “turned off” the CEL. Exact wording on the invoice was ” scan code P04020 Converter Code, ran graph on test drive and passed all test. Cleared Code and ran test, passed”. (I took this as they scanned for codes, but found no errors, so reset the system and re-scanned for error codes but found no errors). $80 later I was happy that there was nothing major wrong with the car. The service manager suggested that a very small “hiccup” in an o2 sensor or some other part of the exhaust system could have occurred and that the CEL can only be turned off after a system diagnosis (it won’t turn itself off even though everything is now OK). Less than 24 hours and 50 miles of driving later, the light is back on. I didn’t get gas since it was looked at (so am fairly certain it’s not a gas cap issue). I was near the dealership when it came back on, and stopped in to let them know it was back on and to see if they could look at it again. The service manager suggested that it may be the converter. Wouldn’t there have been a code that would have indicated this in the diagnostics that they ran yesterday? I’m wondering if they ran only an emissions test and not a full diagnostic? I am curious as to what questions I should be asking before they hit me with a $1800 suggestion of replacing the converter. I would also add that they said that my car passed the “test” after a test drive, but my “in” and “out” mileage are recorded as the same on the invoice! Without going into detail, I have had bad luck with service at this place, but it is the closest Subaru dealer and others are 1 hour+ away. Can you educate me in what I should be asking them to check next? Is there something else that could be setting this off that would not be an error code? My car seems to be running fine. Thanks for any advice you can offer. Thanks for any insight you can provide! 🙂

    1. There is one way to diagnose P0420 and one way only! 90% of the Techs out there have no idea how to actually diagnose the issue properly. It is one of the single largest misconceptions in my industry that the Dealer is the expert, its actually just the opposite in many cases.

      You can read here

      I can almost guarantee the service department did not go to this length and as such the diagnoses was incomplete which is why your car wasn’t repaired.

      The instant they “turned off” the light they also reset the catalyst monitor to NOT READY status meaning the computer is not looking at the catalyst function until the monitor is back on line which is a bout a particular drive event known as a drive cycle. Once the monitor for the Catalyst is back to ready status the catalyst function was looked at by the computer and it didn’t like what it saw in results of testing so it set the code 420 and turned on the light to alert you there is an issue.

      I would suggest the Catalyst has most likely failed but would need some data to confirm.

      Best of luck to you


  153. Hi, after reading all the comments here I hope I can find an answer to my problem. My friend has a 1997 Subaru Impreza Outback Sport, and he has the Check Engine light on for a long time now… I offered to find a solution (Since I’m studying Auto Mechanics), and I took it to my school, were my teacher plugged the device used for diagnosing the engine.. It came out some errors that had to do with the Oxygen Sensors. I checked with my friend and he told me that he changed the sensor once. But then I find out that this car has 2 Oxygen Sensors (One after the Catalytic Converter and one way before it). So Our guess is that the Oxygen Sensor is the problem. I just want to make sure before I proceed to remove that sensor and replace it with a new one that it is the actual problem… Also, what tips would you give me on how to replace it (Especially for how long should I test drive it after I install it, and if it’s okay to unplug the battery to do this…) I would really appreciate the help given, and I wish it can be as soon as possible… Thank you!


    P.S: The car has been running fine since after the light came on, but there’s just one thing that’s wrong… When you stop, you can smell the gasoline coming out from the exhaust… I hope this helps!

  154. The first codes I got were misfire in 3&4, knock sensor and o2 sensor. I replaced knock sensor, o2 sensor, and fuel filter, after i replaced the knock and o2, I got misfire codes for 1&4.

    Idles just fine until you touch the gas and then it just acts sluggish, under load the car wants to stall until the rpm’s get to around 2500-3000. Bad plugs and wires possibly?

    1. Its possible it just needs plugs and wires but there are other possibilities as well.

      You can try the plugs and wires your self and see what happens or you can perform testing to determine exactly what is wrong. Its really up to you how you want to go about it, use nothing but the correct NGK Platinum Spark Plugs Part Number NGK 2300 and good plug wires I would suggest the NGK as well.


  155. your site is wonderful ! you are extremely kind and of big help and I wish I could find a mechanic like you in my living area !

    best regards


  156. We had our 2005 Subaru in for its 160,000 mile service and timing chain. Our check engine light also was on. The service guy said the cable to the evaporator was corroded, which was causing it the CEL to come on. They said they could repair it or replace it — replacing was $600 so we said repair. A few days after having it home, the CEL came on again. Any thoughts you have would be helpful on this problem. $600 sounds expensive for a cable.

      1. I don’t know…what we’ve noticed since, though, is that the check engine light comes on after we gas up. We got a new gas cap, which seemed to solve the problem, but today when we gassed up, the check engine light came on again soon after. Is there some secret handshake you have to do after tightening the gas cap to get the light not to come on???

        1. Ok,

          If the check engine light comes on there is a code set, without a code scanner you don’t know what code is set, without knowing what code is set there is NO WAY to know what system is indicating the problem, if the light comes on even right after fill up but sets a code pertaining to the air injection valve or knock sensor or the blinker fluid replacing the gas cap will do ZERO to resolve it.

          There is no secret handshake only the understanding that it is a complex system that will have a different meaning each time the light comes on. The average driver will never understand this, I have done the best I can in trying to state that the Gas cap is one possibility, but there are others..


  157. Hi Justin, great resource! I have a 2004 Legacy sedan with a 2.5. It runs perfectly except that it pings lightly to moderately (detonates) when I accelerate up even the slightest incline. Also sometimes from a dead stop on a flat incline if I accelerate moderately to quickly. Mostly at lower speeds (25-45 mph). It does not do it at highway speed. It is also probably a little worse in hot weather. Sometimes it will disappear after a second, other times it persists until I get the rpms up higher. Is this normal for these cars? The check engine light has never come on. I should also add that the car only has 19,000 miles on it. It was an old man’s car, and was obviously not used much before I got it. I have used all different brands of gas, and high octane, but the ping still persists. I have a 1998 with a 2.2 which never does this, so I guess I am a little worried I might be damaging the engine. The performance and milage are otherwise perfect.

    1. You may have a faulty Knock sensor, in need of a logic update for the ECM ( engine Control module) a defective EGR system or have some coolant entering the combustion chamber.

      I am speculating on the most common causes, it is not good to allow it to ping it can cause long term problems with the engine.


  158. Hi Justin, I am a long way from you but I have a Subaru problem. My CEL came on today but it is stable.I own a 2005 Subaru Impreza, Engine Type: EJ152DP8AE. I was first faced with the problem of white smoke from the exhaust on startup but only after the car had beed parked at a slanted angle with the right side dipped. Once the car is level in any direction nose up or nose down the car will not smoke. I thought of changing the valve seals, but I am in doubt now. I read on most of the threads and I am wondering if this may be the cause, affecting some component causing the CEL to come on? Car runs smooth and great.
    Need some help.

    1. You need to start with the code number, I am a broken record and I just cant stress this enough the check engine light is an alert to check for codes, the code is than the starting point for an evaluation.

      I wish cars reported codes to the customer but they don’t and you can thank The U.S. Government and the Dealer’s associations lobbing for that.

      Without the code I really have no direction to send you in.


  159. Hi I have a 94 Subaru Legacy and have just replaced the radiator, since replacing the radiator check engine light has been on and fans constantly working. Any idea what I should check first? Thanks

    1. Sounds like the Coolant temp sensor failed, very common after a cooling system service as the instant the sensor is no longer surrounded in coolant it can fail.


  160. i have a 95 legacy 2.2 turbo auto tranny.. i popped a compressor belt and had to drive it home like 2 miles the car would start and sputter and i had to keep the revs up or it would die it and when i would put it in drive the revs would drop even lower and i would have my foot in it all the way and it would barley go… checked the codes when i got home it was p0301 and p0304 so i replaced the plugs and wires and now no more missfire but it still runs like crap.. starts up sputters and dies.. wont stay at an idle just dies unless i keep giving it revs… what do you think it could be… the only thing i think at this point is coil pack or the o2 sensor.. or somekind of sensor pleaseee help!!!!!!

    1. You need to first isolate which cylinder is acting up then figure out why, its difficult to teach you this in a few paragraphs.

      With drive ability issues there just isn’t much I can offer over the net or over the phone. I need factual information about the conditions of systems to know what is wrong, with out that its a blindfolded dart toss at the bulls-eye. You can try disconnecting the mass air flow and if it changes start by mapping its data to see if its out of range. Sorry I can t offer more.


  161. In my 2004 Subaru Forester, the check engine light comes on for a while, then goes off. It’s done this about 7 times in the past 4 months. This is not happening soon after filling with gas, so it is not related to the gas cap. It usually comes on when I am going down a steep, slightly bumpy dirt road away from our house. It usually goes off again about 24 hours later or less, by just not coming on when I start the car. It seems like it might be a loose electrical connection of some sort. Any advice?

      1. Does the light ever come on and off like that simply because of a bad electrical connection, or is it always related to the emissions system. it seems like the light itself is malfunctioning. I need an oil change and will ask the garage to read for a code then too.

        1. Its not possible for the light to malfunction the ECM sets the light when there is an issue, and depending on what system is affected turn it off as soon as its had enough drive cycle events to satisfy it, its different for each and every system.


    1. Thankyou Justine for your time. Checked out the video, out of my scope as a sparky. May as well have a port and polish, change belts etc. whilst the guys are at it. You have put me in the ball park, looks like the previous owners were unawares of a regular maintainance program. Would love to send the head over to you guys but cost restrictive from Australia.


  162. Dear Justin, greetings,

    Mine is a Subaru 1996 Legacy wagon, Both my partner and I enjoy this vehicle even if it’s a little long in the tooth with 186,000 kilometres.

    I have a mate who swears by his Suby mechanic (we’ll call him Ben) but it takes weeks to see him. In the mean time I’m attempting to have a shot at it myself.

    The problem is intermitant, feels like it is starving for fuel or running on 3 or less cylinders, I have had some luck in recreating the fault. It is most prevalant after climbing a slight incline (say 10 degrees) for 200m (this is in the suburbs)at the end of the 200m the road levels out for 50m then a slight decent 5 degrees for another 50 and levels out. For the next couple of hundred m it plays up something awful. With occasional engine stall. I’ve just been informed that it pretty much hates all hills.

    I have changed fuel, oil and air filters, plugs, leads, battery and MAF sensor. The MAF as recommended by another Suby Dealership/Mech when it went in originaly to correct this problem, They also suggested that decarbonizing the valves would be of an advantage, the let some water in through a vac line trick, I have not done this.

    Changing the MAF showed improvement for a couple of weeks, but as in your posts it has taken this time for the sensors to kickin.

    I got in touch with Ben, he sugested checking the fuel tank for impurities i.e. water. I did this with trepadation (yeh yeh I know), as expected there was some slight discoloration on the pump bag filter and some grit at the bottom, I took some samples at the lowest point and found no water.

    This though did have a marked improvement, possibly the pumps electrical connection.

    All well for a couple of weeks, but it’s back and sometimes back fires with the above condition. Q. will the backfiring upset the MAF?

    Today it left my beloved stranded around the corner. I have tried pulling the codes, no luck, the black then green both produce a constant flashing “check engine”. But what I did try today is releasing the vacum in the fuel tank by leaving the the cap loose. This has proved most helpfull. After pushing thru the 3 cyinder thing a couple of times the Suby has not faultered over 50ks of differant terain on the black top.

    Fuel consuption is awfull.

    I’m leaning toward fuel tank.

    I guess Ben with all his toys will be able to sort it out, but in the mean time,

    You opion valued.

    One other thing, I have heard water gurgling in the cab behind the dashboard whilst cournering also intermittant.

    Regards Dan

    1. The gurgle is the clue to air in the cooling system, you may have a HG issue, but if its a 2.2l I would also suspect dropped valve guides, you can verify this by dropping down the y pipe and having a look in the exhaust ports, there is video on our site showing what to look for.