All Wheel Drive Auto: Independent Seattle Subaru Service


Subaru Service Program WVU-31


I wanted to pass along some information that will affect a large number of vehicles, 5 years worth actually.

Pretty much every NA (naturally aspirated) 4 cylinder model from 2006 to 2010.  Essentially the front air fuel sensor is not correctly reaching operational temperature early enough in the start up cycle and until it does the content of the emissions coming out of the tailpipe will be increased over the design.  I do think its great when something that affects our air quality is recognized and dealt with properly such as this.

2006-10MY Legacy, Outback, Impreza & Forester

Subaru of America, Inc. has initiated a Service Program to reprogram the Engine Control Module

on certain 2006 – 2010 MY Legacy, Outback, Impreza & Forester vehicles with 2.5 Liter normally

aspirated engines. Models with 6 cylinder or turbo charged engines are NOT affected.

A modification to the ECM software logic has been developed to improve the performance of the

emission control system. This software change will not adversely affect fuel economy or


This software update is intended to improve vehicle emissions when the vehicle is operated in

cold weather and the engine is turned off and restarted within short periods of time such as in

several minute intervals. The A/F sensor contains a heating element, which is controlled by the

ECM, and which assists the sensor in reaching an optimum temperature, resulting in better

accuracy. When the vehicle is operated under the conditions described above, there could be a

longer than desired delay in the ECM’s turning on the A/F sensor heating element, resulting in

higher than desired emissions. This software enhancement will correct that condition.

ECM reprogramming PAK files will not be available for all models at the time this Service

Program is initially released. PAK files will be available in accordance with the schedule found on

page 4 of the WVU-31 bulletin.

Now because the service campaign will affect a huge number of vehicles Subaru is going to trickle out the letters to Subaru Owners, however if you are taking a vehicle affected in for service you should inquire about having it done to avoid having t make a second appointment when your letter comes.

Thanks for reading



36 Responses

  1. I work at an independent shop & I would like to reflash a 2010 Forester 2.5 non-turbo A/T in reference to the WVU-31 update. I have purchased to CD from Subaru with the files, but the CD does not offer any info on how to. I’m using a laptop with the Bosh Flash-Pro pass-thru. I cant seem to find anything on the internet about this. I’ve done Ford, Chev, Chrys, and others but kind of stump on Subaru. Thanks for any help.

    1. Hi Ray,

      Because we use the Subaru Select monitor with pass through Flash writer, I am not that familiar with the Bosch system. However most likely the file you need is not yet released from Subaru but would be on either the next one or two updates. The file in question is still under the 8 year 80k federal emissions warranty for just about every car, even one over 80k may still have some good will. This prevents a Subaru owner from paying for something they could have done under warranty. Hope that helps



  2. I was looking at buying a 2008 Subaru Forester LL Bean version. But after reading all these negative comments about Subaru, I will rethink and probably buy a different manufacturer.

  3. Hi Justin
    We have just done a Timing belt on A Subaru Forester 2010.
    The idle relearn seems to be taking longer than usual.It has only been three days but normally it is done within the first day or so. The vehicle is a work car so is being driven long distances.Any ideas? I found a reset procedure on the net. We are in Australia.

  4. Justin, does AWD Auto perform this ECU reflash or can it only be performed by a Subaru Dealer?

    Also I see lots of mentions of running higher octane fuels in this article (and comments) and your article on catalytic converter failures. Is this just necessary for higher exhaust temps to clear carbon deposits in the cat or do the Subarus really benefit from the higher octane fuels? (2008 DOHC 2.5 Legacy)

    1. Hello Michael,

      We can and do perform ECM Reflashes every day at the shop, however anytime the reflash is tied to a Recall it must be done at the Stealership as they are the only ones that can record this with the NHTSA.

      Higher Octane fuel result in more complete combustion, which will result in less carbon build up in the convertor which is ultimately what shortens the life of many convertors. What I can share is that in other countries that do not offer the 87 octane fuel there are not as nearly as many convertor failures.


  5. Hi there,

    First I’d like to say that I really appreciate your informative website…I’ve refered to it many times whilst researching Subarus.

    I recently ‘doubled down’ on Subaru by purchasing a used 2007 Impreza SE 5 spd (182,000Km) from a GM dealer in Terrace, BC (The other one is a ’99 Outback). The car had the check engine light on and the cruise light flashing when I test drove it, so I took it to the local Subaru dealer and they kindly did a quick scan which returned a P0301 – Cyl 1 misfire and suggested it most likely needed plugs. They also mentioned that the car had an outstanding recall (but did not specify which one) and otherwise had a good local service history. I decided to take the chance on the car, made the 100 mile trip home in it and changed the plugs (NGK Iridium) myself the other day.

    Last evening, when I went to reset the P0301 code, the car also returned a P0028 code, so I took note but decided to reset the codes anyway (the scanner I have only resets all codes at once). The CEL is out and the cruise control now works, nice! I took it on a short test drive last night and then to work (also a short drive) this morning and I am getting stalling at idle once the car starts to warm up.

    My question is: Does resetting the P0028 code causes the engine to re-map idle settings?

    I intend to investigate the faults that the P0028 code brings up, and to clean the throttle body just in case, possible problems with VVT are a scary thought to this old air-cooled VW driver!

    Worst case, if I can’t figure it out and/or the CEL comes back on, at least the dealer can investigate it when I have the recall work done.

    Thanks again for the great site!



    1. Hello Andrew,

      So yes whenever the “light is reset” what you are actually doing is wiping out the short term memory of the vehicle. The files for baseline idle maps have to all be rebuilt and until that occurs it can and will idle strange and in some cases stall.

      Here are some items to look into

      – Dirty engine oil or low oil levels
      – Clogged or cheap quality oil filter
      – Faulty solenoid, Faulty pressure sensor
      – Failed ECM
      – Open or short in wiring.

      Hope that helps


  6. i’m a mechanic,sounds like suburu is dropping & has dropped the ball many times,especially on my moms 95 legacy outback ,the brakes just went out right now,the next day was fine,(bad design,i didn’t know their was a problem,suburu did, if I wasn’t with my mom she would’ve been in a bad wreck,hurt or killed.)I just replaced the timing belt &water pump, now idles low,will see how it goes.i went to GMI (general motors institute )we’ve been suburu sinse 1995.suburu better get their CHIT together,or nobody will buy their poorly engineered cars.PASS the BUCK.

    1. Hello Mike,

      I want to make sure I understand this correctly.

      You are mad at Subaru because a 20 year old car needs brakes and after you did a timing belt it runs poorly?

      Do I really need to point out that most likely someone used cheap Chinese garbage to replace the brakes in the past and that’s the reason you have an issue now.


  7. I have been reading about the WVU31 issues. I have been looking a purchasing a used Subaru Forester 2006-2009. Your info indicates that the NA (naturally aspirated) 4 cylinder model from 2006 to 2010 is affected. Is the PZEV not affected! I don’t quite understand the difference between the two. Sounds like the PZEV is not affected by the WVU31, is this correct?

  8. I just had WVU31 recall fixed on Tuesday, August 14th. It’s Wednesday, August 15th and my car has stalled and then tonight the cruise control light began flashing and my check engine light has come on. The gas/transmission has been squishy and resistant.
    I’ve been reading that the car just needs to adjust, but it feels somewhat unsafe and unreliable at present, and at no time was I warned that there could be any side effects of the recall. Do I take the car back in or wait it out? There is definitely a correlation despite my car needing minor service because the car ran perfectly with no issues until this recall. Since I am seeing similar if not exact symptoms from other owners it is definitely a liability on the part of Subaru. I can’t afford spurious repairs! Has anyone had any luck on waiting it out or getting these issues resolved??

    1. Joy and whoever else reads this.

      If the Tech doing the reflash does not do it 110% as it should be done, it will have symptoms for a while why the ECM learns an array of data. Some times the Computer wont.

      The only thing you can do is wait it out and deal with the symptoms, or take it back to the Dealer and demand they drive it for the next couple of weeks.


  9. My 2005 Ford Escape was just totaled by not 1 but 2 deer at 60mph…. Handled the incident extremly well but car is totaled and looking at a used pre-certified Suburu Forester 2.5X LL bean edition. Heard so much about Suburu and love the car-like truck look. On Carfax it shows this update to WVU31 recall on 5/11/11. The car was sold by its original owner who seemed like a service guru due to every three months in the dealer for oil, filter maintenance since inception of this new car, right after the recall was done. Ouch, i don’t like what i’m hearing about computer stuff running my cars systems and stalling.

    What to Do!!! Help

    1. Sorry to hear about your Accident.

      As far as computers controlling everything, that is the only way modern cars can achieve the current low levels of emissions that the current laws require.

      We have performed the reflash here and its not a big deal unless not done with a stable battery. There is also a “tender” that can be purchased for $900.00 to help avoid the problems with the reflash that some have had, I would imagine that the techs at the Subaru dealers are either lazy or the Dealer wont spend the money on the device.


  10. I have a 2010 CVT Outback 2.5 and this ECM update killed my MPG. I was averaging 27 MPG on mixed driving. Now I average 22 MPG. I should have bought the V6 engine and gotten better performance at this MPG. I bout the 4 cylinder since it was better on gas.

    I think Honda has a lawsuit on their hands for doing this. This also lowers resell value and is totally selling point is better PZEV for the environment. I’m really disappointed in Subaru. They don’t even have a fix for it.

    I might have to go to small claims court or start a class action lawsuit.

    1. I second that – lets start class action. My 2008 Impreza went from 33 to 29 mpg hwy and 26 to 20 mpg mixed driving after the recall… I almost hate to drive it now. Oh and since it is running rich I had blown headgaskets at 63k – what a POS

      1. Hello Pj,

        Do you feel it was Subaru’s intent to drastically alter your fuel economy in a negative way and anger you? What type of conversations have you had with SOA? Its also unfortunate that the car went from above what it was rated for in fuel economy back to what it was actually rated for as well.

        A HG starting to leak a little oil is not “blown” thats a term from the 1950’s.

        At 63k and years you should be able to get Subaru to cover some or all of the costs as its covered for 5 years and 60k and if its “blown” as you suggest it was bad enough 3,000 miles ago to qualify for a covered repair under warranty.

        Sorry you “Hate” your car.


  11. I had the WVU-31 recall completed on July 10, 2011 when my 2009 Forester had about 59,200km. Up to that point the vehicle had been great with no problems. A day after the reprogramming of the ECM I got a Check Engine Light warning. The dealer checked the code and recommended replacing the front O2 sensor (code po137). I replaced it. Shortly after the Check Engine Light came on again. It actually comes on periodically and then shuts off again too. I took it back to the dealer. Now the error code is P2029 and they recommended replacing the duty solenoid. I replaced it. I asked repeatedly if this had something to do with the recall servicing. They replied no and it was just a coincidence. I don’t think so. The Check Engine Light came on again and it is going back to the shop tomorrow for the 7th time since July. They told me there is no way the ECM reprogramming could have been done incorrectly. They said the car would not run if it was done incorrectly. Is this true? And is it likely that the recall work has triggered this string of Check Engine Light failures?

    1. I am sorry your having issues with your Subaru. I have made attempts to try and explain why this can occur but its difficult to explain.

      But here is the issue, a computer receives new logic or a re flash which changes some of the parameters of which the computer or (ecm) may trigger a fault code for a given system. A sensor that didn’t trigger a fault code based on the current data it omitted back to the ECM may now trigger a fault code because the ECM wants different data now than it did prior to the reflash. I call this the black and white programming the car came with new, the computer also learns and has something called adaptive strategy where it can compensate for data from sensors a bit out of range with the map ( a pathway the computer follows to achieve results based on data received and programming) it has until its satisfied this is the grey area of computing in a modern vehicle and the part that is the hardest to grasp and the hardest to explain.

      Its very much the same as having to go sort out new printer drivers for an old printer when updating to Windows 7 from XP and for some older printers there is no support. Subaru cannot anticipate all of the grey areas when re configuring a new map.

      While I do understand your frustration, but that is most likely what is going on,. I am sure soon the bugs will be sorted out but you can and should also call Subaru of Canada and make sure they are aware of the issue. I am not very familiar with Subaru of Canada but I can only imagine they work similar to how SOA does.

      Its not all that unreasonable to expect that if this becomes a bigger problem Subaru may have to change some of the calibration factors with the new Map another words re think some of the parameters the computer is looking at to trigger codes now that weren’t prior to the reflash. But having said all of that now its also possible that the 02 sensor and the solenoid were working on the edge of specification prior and when the learned data was wiped out there was no more grey area for the ECM to operate in this is something your Forester previously had a 3 year history of.

      The fact that it set a P0137 and then 2029 indicates 2 separate issues and that does sometimes happen. I am sure it will all be resolved soon.


      1. Hi, got the WVU-31 reporgram, now when I use the remote start, the check engine light comes on, brake lights flashes, cruise flashes (and is disabled). Cleared one time at dealer. Ran great tehn when I tried to go into “Pit stop” mode it did the errors again. Could this be one of those that will work itself out? Do I have to keep going back to clear it until then?

        The remote start worked fine until the reporgram.

        1. No there is a bug, cant offer what needs to be done only can say that its not normal and I dont think it will sort it self out. I am assuming the remote start is aftermarket?


  12. i was just reading Ted’s post, and thought i should mention that my dad brought in his 2006 subaru outback for this update, and the very next day the car would stall repeatedly and idle very rough. the dealer told us they cleaned the throttle body and everything has been good since. 200,000 miles now, and plenty more to come! its my dads 4th outback, subaru’s are the best.

    p.s. great website!

    1. Depending on the Dealer, if they don’t do a good job of maintaining the proper level of Battery voltage while performing the reflash The reflash will not go smoothly, this is why in a few cases there are issues, not every Subaru dealer will have made the rather large in vestment into a voltage maintaining device as they can cost over 2500.00.

      Next when starting the vehicle for the first time after a reflash if the Tech is in a hurry and doesn’t allow the relays to cycle it will also cause an issue as well.

      Lastly not performing a drive cycle afterwards because of the FLAT RATE PAY system at a Subaru Dealership also creates a situation where the owner is given a vehicle back that should have been put though some paces prior to releasing it back to the Driver.

  13. I had the software update done on my 2008 Outback and 2 key cycles, ~20 miles later, the check engine light came on. I immediately returned to the dealer and the code was a p0420. The dealer and Subaru both contend there is no way the ECM software update could cause this code. They cleared the warning light, but it came back on about 40 miles later. I took it to my local mechanic and it was the p0420 code again. It just seems way too coincidental. Any thoughts?

      1. So, at first I took your response to mean that you didn’t think it the reflash and the code were connected. However, in the comments of the P0420 post there is talk of reflashing the ECM. Would you recommend a reflash before tackling the other possibilities?

    1. I had the same recall work done in July 2011. the vehicle had been running perfectly prior to that. Since then the vehicle has been back int he shop 8 times for the check engine light. Several emission parts have been replaced since the service manager claimed it is just a coincidence that they all failed immediately after the reprogramming for the recall and the car is now just over warranty. I am pretty well convinced that none of those parts were faulty and it is all linked to the recall work that was done.

    2. I had the same problem. I went back to Subaru to resolve this “coincidence”, and was told that they HAVE NO PEROBLEMS WITH THE REPROGRAMMING EFFORT”, even though the check engine appeared less than 24 hours after??? They could scan (for $180) and repair the car. So I went to Autozone to get a FREE scan. One of the items listed is a Dirty Throttle body. So I put a bottle Throttle body cleaner into the tank, and guess what. Within the magical 24 hours, the Check engine light went off!! I plan to clean the throttle body soon but the car runs with a slight hesitation (sticky butterfly plate on the throttle body). For all the money Subaru gets from its customers, getting repair service recalls is very LOW, combined with the fact that they get an at-a-boy from the government for “voluntarily” issuing a recall on their own???

      1. Hi Steve,

        Most of the issues are from a short test drive or relearn procedure, Had you not added anything and still just continued to drive it most likely the outcome would have been the same.


  14. I just had the service performed here in So Cal on a 2008 outback, there seems to be a problem with the idle speed now, wants to almost stall at very low speeds, forward and reverse, any one else seeing that problem?

    1. It is very common to have a 2005 and newer Subaru that struggles to relearn some of the base idle speed settings and some of the Maps as well. It will get better with driving it in varied conditions.


    2. Yesterday I talked to the service manager about my problem following wvu31 reprogramming (see my earlier post). He told me the engine control module needed to “relearn” some things and that it should get better with driving. He asked me to give it a week and then call back if it hadn’t straightened out by then. If not, they would then clean the throttle body and this should fix it.

      I was about to say “What moron would believe a crock of sh_t like this – let’s just schedule the throttle body cleaning ASAP”. But I held back because I figured if there was any chance of restoring my car to proper functioning I needed this guy’s help – maybe lots of it so I just said “OK”. But after I got off the phone I went straight to the calendar on the kitchen wall and penciled in a reminder to call this guy next week.

      Bored yet? Here’s the interesting part. Today, I started it up and it drove fine – just like my old car had returned – but it lasted less than 5 minutes. It seems that a cold engine idles at higher RPM and this “fixed” the problem until it warmed up. But as I continued to drive, the problem comes and goes. And now it’s normal most of the time. IT’S LEARNING!!!!!

      1. I just bought a 2008 Forester Sport with less than 10k miles on it from dealership. It stalled at the first stop sign on my way to work the next day. Did it again two weeks later (both mornings were below freezing). The service dept told me they had done the wvu-31 reprogramming and I needed to wait for it to “relearn”. I too thought this sounded crazy until I saw your post.

        Please tell me that the problem eventually did go away completely.

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