All Wheel Drive Auto: Independent Seattle Subaru Service


Seattle Subaru Check Engine Light Part II

Your Subaru Check engine light explained part II.



If you haven’t already read the post your Subaru check engine light explained I would encourage you to, as I am only going to try and cover things not already talked about or will be expanding on the previous article.


I have received a lot of comments about the previous post and as I answer Question under Subaru Repair on all experts everyday as well as talking to our local customers.  I have a good feel for what is going through the minds of many Subaru owners wherever they may live. 


The first thing I really want to stress here is that a good thorough analysis of a codes set in regards to a check engine light is always better than plugging in a code reader at a parts house. You can go to the doctor and have your blood pressure checked and they can inform you it’s high, here are some pills or you can have further tests done to determine the cause of the condition and any symptoms.   Knowing the code set in the ECM’s (Engine Control Module) memory is like knowing you have a fever, when why is the answer that is needed.  The choice is really yours to make and a cheap or free check engine light scan does not necessarily equal value.  There is the old saying you get what you pay for.  



Next there are hundreds of possible codes, thousands of possibilities and only one light, can you imagine an airplane having one light for all of its many engine management systems?  There should be a check engine light pertaining to the engine, its sensors and control devices necessary for proper engine function and another light for Emissions control devices and the systems that monitor those devices.  But that is not the system we have nor does it appear that this is going to change anytime soon.


It is far more complicated than most understand, any many cars go without ever being properly diagnosed and repaired.  The biggest area of confusion is that some believe the light comes on at a preset interval, but the reality is there is no check engine light on your 1996 and newer Subaru that comes on at a predetermined mileage or time frame. The second is that some times the light will go on and off for months as a result of programming, monitors, drive cycle events, temperature and the nature of electricity.  Most of the time the car will seem to run ok and that is a result of what is called adaptive strategy, this is the ability of the ECM to overcome faulty sensors, intake leaks and even some misfires.   



I would say that less than 35% of the industry actually understands how an OBDII system actually works and I guarantee you that not one person behind a parts counter with a code reader understands what a catalyst monitor is and what are the parameters of the monitoring system.  So why should they give any advice at all in regards to a check engine light, is there any value in there opinion?   In the portion of states that have a vehicle emissions programs the Technicians that are licensed by the state to diagnose and repair emission related problems are a leg up on Technicians that are not required to maintain there license and thus their education.


The Check Engine light is more about the Emissions systems on the car then it is the actual engine itself.  If the Technician working on the car is not an Authorized Emissions Specialist he or she may not have received the proper training or is defiantly not going to be as up to date as a Technician that is staying current.  I often find that when I talk to my customers about what is truly involved in the diagnoses and drive cycle after repair, most had no idea just how complicated it can be to truly diagnose, repair and than verify that repair.  


The check engine light comes on and a code is stored in the computers memory, the engine may or may not feel any different.  this is really where the confusion starts.  A loose gas cap can cause a “check engine light” but what on earth does the gas cap have to do with the engine?   I wish there were two lights and two legs to the the system one being a check engine light and the other being the check emissions light.  But the federal government was afraid of creating confusion with multiple systems, yes in 1996 The government decided we needed a standardized system. I agree that we needed some standardization , but the intent was to clean up the air and this attempt has largely failed.  The single biggest problem is lack of enforcement.  I hear so often that a Dealership told a driver the light was no big deal when the real secret is there are a lot of items on a newer car that are under warranty for a much longer period of time than most drivers are aware of.  Or I hear about a check engine light being on for three years with only maybe some confused partial attempt at repairs usually done by scanning it at the local parts store and installing one or two suspected “bad ” parts.      But there is only one light and there is no way to know if the check engine  light is on because of a loose gas cap or a failed coolant temperature sensor without a proper diagnoses  or at a minimum a code scan, one will let excessive hydrocarbons into the atmosphere in the way of raw fuel vapor and the other may leave you stranded.  


Here are some tips for 1996 and newer Subaru vehicles that will hopefully help.


On the dashboard of your car there are many different colors of light.  Lets break down the different colors and what they each mean. The turn signals are green and just like a traffic signal green means go.  The check engine light, ATF temperature light are yellow and yellow means proceed with caution.  The oil light & battery light are red and mean stop driving the car.  The additional aspect of the check engine and transmission temperature lights is the ability to flash which is basically an indication to stop driving the car.   If your check engine light starts flashing you need to have the car looked at as soon as possible.  


Consider purchasing a basic code scanner yourself if you have a diagnosed emissions related problem that you cannot afford to repair.  For example a Catalyst system may cost upwards of $1200.00 to repair and that could be a hard pill to swallow.  But since there is only one light how will you know if anything comes up? This is when I suggest a basic code scanner, if something new comes up on a weekly or biweekly scan you will know to have it diagnosed.   Keep in mind a code is only the starting point.


There are two different types of codes component and conditional codes, here are some of the most common codes we deal with and the process that needs to be done to truly get to the bottom of the code.


P0440 Evaporative emissions leak.  The ECM monitors the Evaporative system pressure and through the monitoring system believes there to be low or no pressure, the most common cause is a loose gas cap but a leak any where else in the system can cause this as well, typically a smoke generation machine is used to look for leaks in the Evaporative Emissions system A smoke machine can cost over $1000.00 and has on going cost in the way of the what ever is used to create the smoke such as mineral oil.  So why on one hand a loose gas cap is pretty easy to figure out, connecting a smoke machine to the proper ports in the Evaporative Emissions system then look for leaks, the Evaporative system runs from the fuel tank to the engine compartment stopping at the purge canister, vent solenoid and other components as well.  If no leaks are found there are other possibilities such as electronics not turning on or off as they should.  This could be anything from a failed solenoid, faulty wiring or problem with the vehicles computer. 


P0420 Catalyst efficiency below threshold.  My favorite, Here is why the code is set.  Starting in 1996 every vehicle for sale in the U.S. had to have a way of monitoring Catalyst function.  The job of the Catalytic Converter is to take Carbon Monoxide (a by product of internal combustion) and convert some of it back to Oxygen, this is done with three precious metals, temperature & fuel mixture.  There is an Oxygen Sensor, or O2 sensor mounted in front of the Catalyst and one after.  The ECM (Engine Control Module) uses data from the O2 sensors to know if the Catalyst is doing its job of creating Oxygen.  Now the ECM does not constantly monitor the Catalyst system, this starts to get a bit complicated but depending on how the vehicle is being driven it is not always possible for the Catalyst to function properly as such in the ECM’s programming it will only monitor the Catalyst function after certain events have been met in a drive cycle.  Once the ECM is looking at Catalyst it uses the voltage values created by the front and rear O2 sensors to determine if the Catalyst is working with in the programmed threshold.  there are a couple of ways to properly test a Catalyst, but the most accurate way is to do a Catalytic Converter efficiency test.  This test involves running the vehicle until it is up to temperature, then install a 4 or 5 gas analyzer probe into the tail pipe of the exhaust, then shutting the vehicle off, disabling spark and fuel (to keep the vehicle from starting), injecting propane into the intake manifold, and cranking the vehicle over and obtaining the readings from the gas analyzer.  The reason for the test procedure is to remove the ECM, Mixture and O2 sensors from the loop, to purely test the Catalyst’s ability to function and it is a pass or fail test with a few Grey areas.  It is not possible to simulate this test with a generic scan tool in the Auto parts store parking lot.  A failed Catalyst is just one of many possible causes of this code and at the time of writing this article the list price for a one piece Catalytic Converter (found in most 1999 to 2004 models) from Subaru was $974.00 not including labor or gaskets.  If the Catalyst is not the cause which is very possible and the culprit is a O2 sensor there are other possible ramifications of not repairing the vehicle properly. If the Catalyst has failed, reasons as to why need to be investigated to avoid a quick repeat of the failure.  The number one cause we see at the shop is a failed head gasket allowing coolant into the exhaust and degrading the Catalytic Converter and or 02 sensors.  But we have also seen contaminated  gas, slow O2 sensors, and Mixture problems cause this as well.  You have to remember the Catalyst function is measured by the ECM as seen through the “eyes” of the O2 sensors.  If you live in Washington State and fail an Emissions test as a result of a check engine light and a PO420 code set, you can request they perform a tail pipe test and if it passes so should your car.  Why is this?  There is chatter that there is a disconnect in some cases between oxygen content in the exhaust and cars that will still run below the legal “measured” tail pipe Emissions standards for that year. 




In Washington state there is a limit an owner has to pay to obtain a waiver in lieu of making a vehicle pass the test and the vehicle is tested every 2 years.  The repair waiver is is granted as long as repairs and or diagnoses are done in the attempt of making the vehicle pass and this work is done by an authorized Washington state department of ecology emissions specialist.  This only applies to unmodified vehicles and is up to the state to decide if you qualify.  Other states have similar programs, and you should check the department of ecology website for the state you reside in for current information. 


P0301, P0302, P0303, P0304, Cylinders 1 through 4 misfire also usually a flashing check engine light will occur as well.  On a second generation Subaru Engine the most common cause would be spark plug tube seals that have allowed oil onto the spark plug wires and plugs, but we also see a fair amount of failed coils, plug wires, spark plugs and some models with an injector failure.  From there a burnt valve, broken ring, rodent chewed wiring and gasket leaks are all examples of things that can cause a misfire code as well.  A flashing check engine light really means you should not drive the car as damage can occur to the Catalyst, rod bearings, head gaskets and the list goes on. 


So one day the light comes on and the gas cap is found loose, but the next time the light comes on tightening the gas cap doesn’t fix it.  Frustrated vehicle owners take cars in to have the check engine light  repaired and it is, for a couple of months but then comes on again.  The owner than takes the car back to the shop where the service advisor, owner  or Technician has the task of trying to explain that most likely its just a new problem.  This is a very common situation that happens and there are a wide variety of reasons as to why this happens.  This is one of the single biggest reasons you should have a place you take your car to for all your service needs.  Taking it to shop A and then to shop B three months later will typically not yield the best results.  If you have lost confidence in a shop on a repeated check engine light situation that is understandable.  A good repair shop will document what codes are set each time the car comes in what was done to diagnose and or repair the condition if it is a different code each time it is most likely a different issue each time.  If there is an ongoing issue keeping one shop involved is a better way to go in most cases.   There are always exceptions to this and only works if the shop you are taking your car too is familiar with the brand.  Sometimes it takes a significant amount of time to diagnose certain conditions that may trigger a check engine light.  A general repair shop is going to have a disadvantage in some cases over a specialist in one make of vehicle.  As we specialize in Subaru we have a huge advantage over the shop down the street that works on every type car that comes in.  Dealership service departments are all about profit and productivity and are generally a bad choice for a problem child that will take a lot of time to get to the bottom of, its just not what they are good at. 


Auto repair is not an exact science, sometimes a good diagnoses is a process of elimination and can be very time consuming as well as frustrating for both driver and shop alike, but it doesn’t have to be that way, a better understanding about how the systems actually work can go along way to clearing up confusion.


34 Responses

  1. Hello Justin,

    I have a 2011 Subaru Outback. I’ve had it for about 4 months. It’s in need of an oil change, I did change the filter a month ago. Today I got in and immediately new it wasn’t driving right, look at my dash and saw my check engine light on and my brake light flashing. I didn’t want to drive it, was worried I would make things worse. But I was stranded. Decided to drive about a mile down to auto parts store for a quick diagnostic test for codes. I got the error code for cylinder 4 misfire. I was surprised I didn’t see anything referring to the brake light on. I have read vehicles and set off misfire codes when rear drum brakes are an issue. The brake light came on once before, not flashing. But immediately went away. Then a month or so later we have had some squealing on and off. The car only has 57,000 miles on it. We are on a very tight budgets, bought this car knowing we needed one that was reliable. The other car is a clunker and just had to send two older cars to the junk yard because they weren’t worth fixing and we had already put way too much into them.

    I would love you input.

    Thank you

    1. Hi Tanya,

      So you have a check engine light that is on and flashing, had it scanned and know you have a misfire from cylinder # 4.

      Misfires and brakes seldom have much to do with each other, most likely its a plug, coil, injector or something more serious, but no one will know for sure until its properly diagnosed, and that’s really the next step.


  2. Hello, I’ve got a 1995 Legacy L 2.2(130k) with a p0400. I’ve cleaned the throttle body, the egr valve (tested good)and pipe. I replaced the bpt and egr solenoid as well as all the small vacuum lines. Cleared the code and it came back in about 80 miles of driving. All other monitors are ready after driving awhile, no other codes. My question is can a leak at the pcv hose cause loss of vacuum pressure in the egr system? Would that trip this code?

    1. Hi mike,

      If you have verified the EGR function is good, you must evaluate the EGR monitoring system next with uses pressure differential to monitor EGR function on a 1995. Look at the function of the pressure sources sensor and the pressure sources switching valve passenger side strut tower.


  3. Hello Justin,

    I have recently had my alternator fail on my 2011 Suburu WRX, this lead to my battery failing and had to get both replaced. Only a few miles after the replacement I had my CEL come on and the Converter operating below threshold code came up. I am wondering if I in fact need to get my converter replaced as my dealer said or could it be a damaged sensor?

    1. Hi Cameron,

      If the car has less then 80,000 miles, the convertor is still covered under a federal emissions warranty.

      Did the dealer fail to mention this or does it have more then 80k?


  4. Hey Justin,

    This is a adventurous story about my check engine light: I have a 2002 outback llbean with ~115K on it. The CEL came on several months ago (roughly at 110K) with code P0051(upstream O2 sensor, driver’s side). Recently I decided to not ignore it anymore and have the sensor replaced, the code was gone but after about 5 miles while I was still driving the CEL started to flash, and the car was vibrating, having hard time accelerating… I pulled over and run the computer following codes came up:

    P0302 – Cylinder 2 misfiring
    P0304 – Cylinder 4 misfiring
    P0306 – Cylinder 6 misfiring
    P0106 – Manifold Pressure Sensor Circuit Range Problem

    Then I cleared the code, restarted the vehicle and codes were gone. I drove for about a mile and everything worked just fine. Right now I just don’t drive it cause I’m afraid that the codes will come back.

    I bought the car 2 years ago and it only has a P0038 problem in the past 2 years.

    So my questions are:

    1) Why is this happening? cylinder 2,4 & 6 are on the passenger side, some people say that I should get both front O2 sensor replaced, is it true? Oris it possible that those misfiring and pressure sensor codes just mean that the computer is readjusting itself after the O2 sensor replacement?
    2) What should I do now? Now I know it is wrong to ignore the CEL (lesson learned), but does this situation mean some serious problem is happening to my car? should I do a tune up anyway?
    3)Any more suggestions and advice are greatly appreciated!


    1. Hi Sue,

      I wouldn’t really be able to tell you whats happening with out seeing the car, there are just way to many possibilities.

      Id start with checking the “sensor repair”, may be something came loose, its wise to not drive the car with the misfires, and Id also look into the possibility of an air leak.

      So basically what I am saying is it needs to be diagnosed by someone locally.


  5. Justin,
    I have a 2004 Legacy SW. It had only 18k on it when we got it about 5 years ago. Now has about 70k. Reading you blog helped me resolve another problem I had about 18 months ago.

    I am getting the midfire codes on 2 cylinders. It misfires only on a cold startup; runs and starts fine when warm. I took 2 long trips with the car; the problem cleared up for a couple of days then reappeared.

    I saw your recommendation on the spark plug tube seals as being the most common cause. And in a comment to another person you mentioned a few fillups with high ocatane fuel.

    I’m deabating on whether to try replacing the seals first or using high octane fuel first. What about fuel injector cleaners?


    1. Hi Mike,

      Inspect the tube seals and plug wires if leaking and the wires are now oil, start with replacing the wires, plugs and seals, if they are dry look else where.


  6. Hello Justin,
    I have a 2004 legacy 35th with a 2.5. It only has 57,000 miles. It previously belonged to an old man that hardly drove it. For the past three years I have driven it in more normal circumstances with no problems up until now.
    I recently received the P0420 code. I brought it to my local mechanic who diagnosed it as definitely being the converters. He said that the sensors all appeared to be operating properly. This car has 3 converters and 5 o2 sensors, it might be a California emissions vehicle, even though it was sold new in New York.
    A couple of questions: is it really impossible to detect which exact converter is at fault as my mechanic claims, and if so, what is the typical cost to replace 3 of them? My mechanic said I could drive the car this way with no problems, although I now don’t have cruise control. (West Virginia is rather lax with emissions). Is there any way I could determine this myself as I am not sure I can find a mechanic such as you around here that would be familiar with Subarus.
    I also asked him if there was anything wrong with the car that would have caused a converter failure to happen after 57,000 miles and he said the car was running perfectly and sometimes age is a factor. I have never had a check engine light come on in the time I have owned it and take meticulous care of it. I wish I lived closer to you so I could bring it in, but, unfortunately, West Virginia is a little far.
    Thanks for any help you could give me.

    1. Hello Evan,

      Id try a fuel induction type service, three to four tanks of premium fuel and some spirited driving and see if you cant get some heat out of the convertors. What your guy is missing is that a ten year old car with 57k on it is going to be full of carbon build up form how it was used.

      Unless you separate and sample the readings from each Cat while performing a convertor efficiency test with propane and a gas analyzer then no the cats are not being tested separately and its just an educated guess, one that we sometimes will also make if it doesn’t look like the exhaust will come apart and go back together for us.


      1. Hello Justin,
        First of all, thank you for your response to my original question.
        I thought I would post a follow up to my 4020 code problem. As it turns out, my car has the ULEV emissions which are covered for 15 years/159,000 miles in New York, where I (fortunately!) have a second residence. I took the car to a Subaru dealer in New york who, in addition reading the 4020 code also read a misfire code caused by oil leaking in to the spark plug tubes. After replacing the valve cover gaskets and wires, he drove the car 20 miles and there has been no repeat of the 4020 code…so far.I will pick up the car tomorrow. My question is, would these misfires simultaneously set off a 4020 code, and would that cause permanent damage to the cats if that is the cause, or could the cats survive that? It probably went on like this for a couple of months, unfortunately as I don’t think it was properly diagnosed by my mechanic in West Virginia. (It might be time to find a new mechanic). Many thanks in advance for your response.

        1. Hello Evan,

          Misfires can damage the Convertor. If there is a misfire the readings from the 02 sensors will be off and its possible it was never an issue.

          However it will take more than 20 miles to reset the catalyst monitor to ready status, the ECM to begin testing the efficiency of the Convertor. It may take a month as its about conditions not miles.

          So we are not out of the woods yet I am afraid.


  7. Taking 2006 Outback for overdue oil change with P0026 check engine light with alternating “cruise” light five miles after start up. P0026 Intake Valve Control Solenoid Circuit. #1, open or short circuit condition, #2, poor electrical connection, #3 faulty intake valve control solenoid. Hope it’s just a poor connection. Will ask more questions if “more-than simple fix” is required. Thank you.

    1. When you go to long on oil changes you will encounter issues with the oil level or filters becoming restricted, this can and will cause the symptoms you have.

      Most likely all you need is an oil change and to have the codes cleared, I would suggest better service in the future however.


  8. Excellent article Justin, the best I’ve seen written on the subject. I’m in the midst of a P0420 now, at this point I suspect the O2 sensors and was going to replace the rear one. I have an ’05 Forester X. I called my local Subaru dealer (I’m in Ontario, Canada), he said they used 2 different O2 sensors that year, and from my VIN they advised mine was an early model and the sensor was $445 cdn. If it had been the later 05 model, it would be $225 cdn.

    I’m wondering if O2 sensors can be removed and cleaned somehow, based on the history below.

    Basically, the following repairs in order were performed:
    – Leaking head gasket (removed engine, replaced both)
    – Replaced spark plugs
    Even though the CE light was flashing (0402), it passed a tailpipe emission test.
    Over the course of the next few months:
    – Misfire codes and 0402 were coming up
    – Replaced the cat w/an aftermarket direct fit one
    – Replaced the wires
    – Replaced the coil
    At this point, put premium fuel in and added injector cleaner for the next 6 tanks. The CEL went out the first tank after 50 miles, came back on at 90 miles.
    – still flashing P0402
    Hence my hope that the sensors can be cleaned to avoid buying that costly one.


    – Replaced the Coil

    1. Hello Kerry,

      Thanks for the kind words.

      Misfires will damage the Catalyst pretty quickly Im afraid, and if you are still experiencing any misfires I would look into dropped valve guides as one thing to inspect. If the misfires are resolved you can replace the Sensors and drive the vehicle in a way to build up heat in the exhaust and you might bring some new life to the Convertor.

      As far as cleaning the sensors, they tend to break down internally more so than become coated. Think of the sensor as a rechargeable battery, after so many years of heat up and cool down cycles much like a charge and discharge situation in a battery eventually the range or capacity become limited and no longer to the thresholds or limits that are needed to function.

      And yes there is a huge disconnect between a tailpipe test and convertor function during convertor monitoring by the ECM.

      By the way Im pretty sure we could ship you sensors cheaper than that, if you fill this out here we can give you a price.

      Hope that helps


  9. Hi Justin,

    I have a 98 Outabck 2.5L. The code reader is telling me that there is an open in fuel regulator circuit. Please point me in the right direction in terms of further diagnosis/what the possible cause of this code is. The car runs fine but the check engine light is on.



  10. Thanks for the info on the PO420 code. My Toyota RAV failed emissions today due to a PO420 Code. Living in Washington State, I was excited that you recommended requesting that they do a tail pipe test. However, I contacted the Emissions place and they say that they are not allowed to do a tail pipe test for anything newer than a 1995 vehicle. I thought you should know…

    1. Hi Jeff,

      Its not as Black and white as that.

      A Tailpipe test can be substituted at the station managers discretion, upon documentation by an authorized emissions specialist has deemed the Catalyst function Ok. This may also be initiated by a Department of Ecology employee, this is also known as “Refereeing”. Because the program is not to be a “tax Burden” on those that cant afford a repair this is one of many gray areas with in the system in Washington State. Sometimes this can be done by drivers request, but only if the station manager is aware of this and is at least involved in the process.

      I know its possible because I have forced it to be so many times in my career, is just not easy.

      The employees at the Test station are temps, and its a revolving door, by the time they leave they may have seen a few things, but catch even the manager on “month two” and you will have different results then someone who has been around.


  11. Interesting notes on the p030x. I just popped a solid CEL with P0304.

    This happened as it has started to get cold in the morning and when we first start the vehicle it shudders and sputters like not all cylindars are firing. Once I give it a few seconds, then rev, everything seems fine. If the car is “warm” then startup is fine, but if left for a few hours same problem with idle hesitation at startup. P0304 was code I pulled (cyl4 misfire of type1). Solid CEL. I do clear, but it comes back after a couple of drives….

    I am looking to help narrow this down before taking in, and was planning to pull plugs, then swap spark plug wires to see if problem follows wire/etc… I did have an overheating condition happen last year that took me a bit of time to resolve- finally narrowed down to the thermostat (this was very intermittent), and also replaced radiator cap, and hose line to expansion tank (saw a split, so not pulling liquid back into radiator when cooling).

    Anyway, wrt to the comments on burnt/damaged valves, would a dry compression test validate that these were okay so I can move onto something else as the culprit? More curiously, how can I prove (yes or no) this is a HG issue? I am just deeply suspicious of the cooling system as I seem to lose random amts of fluid on a, yes, random basis – and yet a liquid combustion leak test kit (napa) is not showing anything as far as I can see. No visible leaks. Oil is good – just changed it last weekend. And yet… there seems to be a sweat smell from the exhaust when started in the morning that clears up….

    116k miles – and NO I have not yet changed the timing belt (but still looks good) as I was hoping to make sure the high heat issue was resolved in case it was a HG – in which case doing these with the timing belt would be most cost effective.

    Any advice appreciated….

    Also, if you happen to know a good subaru specialist in the bay area, I would be interested. I have a few leads on a couple from some other subaru owners I trust….



  12. Hi Damien,

    Thats a pretty big list. Gotta stop driving it if the temperature gauge is moving off of its normal position.

    A blinking check engine light is another reason to stop driving it, until you can have it diagnosed locally.

    Because the misfires are all cylinders and there is no lean or rich code set in correlation its going to be a challenge , the P0420 is most likely being set as the catalyst cant function in the state the car is running in now.

    The only real advise I have is to have it looked locally by a Subaru Guy.


  13. Hi Justin,
    Nice post. I have a 2002 Outback LL Bean 3.0 H6. OBD II is showing the P0420 as well as the P0301 thru P0306. The check engine light usually blinks for a few seconds after a cold start, during which the car shakes a little…then it settles down, the CELight goes solid and everything seems normal. Also, not sure if this is related, when idling the temperature goes very high, sometimes into the red. Do you have any suggestions for where to start looking? Thanks!

  14. My husband replaced the O2 sensor because the CE light came on code P0032 ce light still on code P0032 HO25 bank 1 sensor 1 heater circuit high any suggestions??

  15. I got my 2004 WRX inspected this weekend (not by a Subaru dealer), and now the Check Engine light is on, constantly. I am taking it in to a Subaru place for an oil change – is this something that is normal and easy, or a big UH OH? I know you can’t tell without seeing the car, but what’s your first thought? Thanks

  16. Thank you for an excellent post about the check engine light. I have a 2000 Subaru Forester S with a frozen odometer reading of 207,098 miles on it. CEL came on when the cruise control/speedometer/odometer died.

    Mechanic told me that the speed sensors in front and rear needs to be replaced, so I’ll go back next week when they get the parts, but after reading your post, I emailed the mechanic asking what codes showed up during the diagnostics. Unfortunately there are no Subaru experts in these parts (west Texas in the land of Chevy & Ford trucks)… It would have been nice to bring my car to your shop.
    Laura B.

  17. I’m having a problem with my wife’s 2004 Outback 2.5l. It was due–now overdue for inspection, service engine light was lit. I’m pretty handy, have worked on a wide variety of autos etc. It coded out to the downstream O2 sensor, which I replaced and pulled the negative battery cable to reset the light, which it did. Now though, I’ve put over 100 miles on it on at least a dozen drives and it will not recognize the catalytic and evap monitors. For the emissions inspection, 2 unrecognized monitors will result in a fail. Since I DIY’d it, I do not have enough money spent on it to get a waiver. I’d have to pay a shop to fail it, then they have to get a waiver, then do the repairs that have already been done, then turn it over to me to drive until it recognizes the monitors … Crazy! At this point, it has not been inspected, if i can get it to recognize the monitors, all is good. Chilton’s states that it requires 40 on/off cycles each with at least 40 degree temp gain and reaching 160 degrees for it to recognize the monitors. This seems way too many. Have you encountered this, or is there a step or something I’m missing?

  18. I have a ’98 Subaru Legacy RH drive. The check engine light comes on after approximately 20 minutes of driving. When it comes on, my brake lights stop working. What’s the connection between the two ???

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