CEL P0031 or P0032 Fix
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This is a discussion on CEL P0031 or P0032 Fix within the Maintenance, service, and repair forums, part of the Tutorials & DIY category; Ok, so for about the past month, I've had a P0031 or P0032 CEL popping up everytime I drive the ...

  1. #1
    Registered User tubbytreats's Avatar
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    CEL P0031 or P0032 Fix

    Ok, so for about the past month, I've had a P0031 or P0032 CEL popping up everytime I drive the car. I turn the car on, and boom, there's the CEL! After pulling the code with my AccessPORT, I found this.

    CEL Details:
    P0031 - Front oxygen (A/F) sensor heater circuit low input
    P0032 - Front oxygen (A/F) sensor heater circuit high input

    So after allowing it to annoy me and fester for the past few weeks, I decided to get proactive and fix things. I read up on Nasioc.com and ClubWRX.net all I could find about these CEL's and the findings were really slim.

    Some folks talked about how they had to replace their O2 sensor, and just paid their local dealer to perform the replacement. Others tried using a multimeter and checking resistance between all of the (4) leads going from the engine bay wiring harness down to the O2 sensor in the exhaust manifold "Y" pipe. (Yes Snowvert, where the stock headers meet up before the uppipe. )

    The O2 sensor in your exhaust manifold actually is labeled as an (A/F) sensor, and the rear O2 sensor behind your last catalytic converter is actually a true (O2) sensor. I priced out a replacement sensor for the front, and on http://www.SubaruParts.com they wanted $153. (YIKES!!) For the rear O2 sensor, it's like $114 or so.

    Anyway, I wasn't about ready to walk over to Wagner Subaru and hand them a few bills and let them have at it. So I went back to AutoZone and rented an O2 sensor socket and went to work!

    After getting inside the engine bay and unplugging the wiring harness for the O2 sensor, I then crawled underneath the car (which was on ramps) and got behind the passenger-side front wheel where the O2 sensor is located. I removed the sensor (with a bunch of needed force, there was serious corrosion on that exhaust pipe going on...) and noticed that one of the (4) wires had melted clean through!

    I realized that when I did my uppipe install with a friend, there is a metal bracket that attaches to the O2 sensor wire and also gets bolted to the engine block. This bracket keeps the O2 sensor wire in the right place and keeps it from getting melted by exhaust heat from the heat shields. Because that bracket never got re-attached, my O2 sensor wire was dangling dangerously close to the engine block and melted through!

    I took a quick trip to Radio Shack with my roommate and we got all the necessary items we needed to solder a patch wire in and fix up the harness. Plugged it all back in, and voila, no more CEL P0031 or P0032! What a deal!

    I feel like a million bucks today, and driving to work without a CEL for the first time in a month felt really good. (Gave me reason to speed like a maniac too! )
    Last edited by tubbytreats; 10-08-2004 at 08:13 AM.

    2002 WRX Mods:
    AP Stage2/93, ScoobySport Up, Dp, & Muffler, SS AutoChrome TMIC, Hawker PC680T Battery, Injen CAI, ACT Stage2 Clutch, Gruppe-S 13.8lb Flywheel, Mobil1 and Redline oil, NGK BKR7EIX plugs, Goodridge SS Lines, Motul RBF600, Hawk HPS pads, 35% 3M tint, Koji Headlight Mod, SilverStar Bulbs, Blaupunkt MP3000 headunit, Infinity BassLink Sub, Kenwood KFC-1689ie speakers (6.5"F / 5.25"R), Rota Downshift (Black), Yokohama AVS ES100 (225/45/17)

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  3. #2
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    O2 Sensory tool

    I had a go at changing my front O2 sensor tonight and got screwed. I didnt have the tool and could not get to sensor anyway I tried. What pain in the axs. I dont know why subaru doesnt put a notch in the heat shield so you can actually pull it off and get it out of the way. Anyway, long story short I clipped the wires on the sensor thinking I could get a deep socket over it...not go. So, now Im driving without an O2 sensor at all. Im in Juneau Alaska at the moment and I dont think I can get a shop to rent me a tool...but out of curiousity was it just a socket with the side cut out? Any other pointers to get this job done with less blood and tears?

    Thanks
    Adam

  4. #3
    Registered User tubbytreats's Avatar
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    Sorry to hear about your frustrations.

    The O2 sensor socket I rented did have a cutout along one of the sides of the socket, so you could feed the sensor wires through it and still turn the nut properly.

    A new O2 sensor is about $150 from a dealer, it is unfortunate you cut the wires (unless you think you can repair them later and that the sensor is still good)

    2002 WRX Mods:
    AP Stage2/93, ScoobySport Up, Dp, & Muffler, SS AutoChrome TMIC, Hawker PC680T Battery, Injen CAI, ACT Stage2 Clutch, Gruppe-S 13.8lb Flywheel, Mobil1 and Redline oil, NGK BKR7EIX plugs, Goodridge SS Lines, Motul RBF600, Hawk HPS pads, 35% 3M tint, Koji Headlight Mod, SilverStar Bulbs, Blaupunkt MP3000 headunit, Infinity BassLink Sub, Kenwood KFC-1689ie speakers (6.5"F / 5.25"R), Rota Downshift (Black), Yokohama AVS ES100 (225/45/17)

  5. #4
    Registered User schrags's Avatar
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    Just got this CEL on saturday on my bugeye. I checked the connection and that bracket that holds it off the engine fell off from the bolt somehow. Took it out and the the wires were still intact so I just went to the dealer and bought the a/f sensor for 200 bucks instead of just saving 30 bucks online and waiting a week. Put it in today and no CEL, back to normal. Easiest way to get that bracket bolted back on is to just take the intake and the air box out IMO.

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    Sorry for bringing this post back from the dead, just checking if you had the service semantic when you changed out the front o2. I'm sure if i climbed under the car i could recognize everything. I just like looking at everything on paper before i actually climb under the car.

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    P0031

    Quote Originally Posted by schrags View Post
    Just got this CEL on saturday on my bugeye. I checked the connection and that bracket that holds it off the engine fell off from the bolt somehow. Took it out and the the wires were still intact so I just went to the dealer and bought the a/f sensor for 200 bucks instead of just saving 30 bucks online and waiting a week. Put it in today and no CEL, back to normal. Easiest way to get that bracket bolted back on is to just take the intake and the air box out IMO.
    SO YOU REPLACED THE MAS WITH THAT CODE AND IT WENT AWAY? ARE U TALKING ABOUT THE BRACKET THAT HOLDS THE 02 OR THE AIR BOX? WAS YOUR CAR HESITATING UPON ACCELERATION?

  8. #7
    Registered User schrags's Avatar
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    Quote Originally Posted by my2002wrx View Post
    SO YOU REPLACED THE MAS WITH THAT CODE AND IT WENT AWAY? ARE U TALKING ABOUT THE BRACKET THAT HOLDS THE 02 OR THE AIR BOX? WAS YOUR CAR HESITATING UPON ACCELERATION?
    I replaced the front oxygen a/f sensor. It is located in the front exhaust manifold that you can gain access to by through the plastic fenderwell when you take the front right passenger side wheel off. It is pictured here ScoobyMods - View Single Post - BEST DAMN WRX DOWNPIPE UPPIPE install cobb stage 2

  9. #8

    Peachypumpkincheeks

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    New Questions!

    So I finally got my CEL checked at Advanced Auto Parts, and I too have the P0031 code. Not being as technically suave as the rest of you, I still have several questions. I searched and read a TON of information, but a lot of it was regarding people replacing the O2 sensor themselves. Which leaves me still confused, as this is a feat I certainly cannot attempt myself. Soddering?

    The AAP guy asked if I wanted him to reset the comp and I said no. I figured it would pop up again so let it serve as a reminder. So here are my questions:

    1. Is this issue hurting my car, or is it just causing me to use more gas?

    2. Is this a common problem on a stock WRX?

    3. If I upgrade to Cobb Stage 1 or 2, will this take care of the issue or will I still need to replace the sensor?


    Any advice or feedback you guys can give would be super helpful. Thanks!
    Heather | 2002 WRX | Stage 2
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  10. #9

    Peachypumpkincheeks

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    Knowledge is fun!

    So after more reading and asking questions, I kind of understand more about this error now, and I think I can answer my own questions:

    1. It's not hurting my car persay, it's just forcing my car to run off preset A/F codes if it's not getting a read from the O2 sensor. However, my car is not running optimally and I should get this issure fixed.

    2. Seems like this could happen to any vehicle at any time, it's just more common amongst modified cars.

    3. The sensor will need to be replaced regardless of upgrading my map.

    Oh well, I read it's like $114 to replace, so now I just have to find a reputable shop.
    Heather | 2002 WRX | Stage 2
    ScoobyDMCtt | Official Bodyguard #2 for the Bugeye Mafia
    TastesLikeAwesome | @Subiestar

  11. #10
    Master Baiter EJ257's Avatar
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    I Support ClubWRX
    Quote Originally Posted by Speedette
    3. The sensor will need to be replaced regardless of upgrading my map.

    Oh well, I read it's like $114 to replace, so now I just have to find a reputable shop.
    I'm friends with a local dealership parts manager - shoot me a PM with your zip code and I'll see if he can give you a better priced shipped
    2005 WRX STi (Mods | Virtual Dyno)

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  12. #11
    Registered User Fahren's Avatar
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    Bumping an old thread.

    has anyone replaced the front o2 sensor with no luck in removing the CEL?

    i just spent the $215 for the o2 sensor and to no avail.

    i had p0032, and p0031, got rid of the 32, but still have the 31.

    any ideas?
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    Fahren, what year is your car?
    i had same code came up 2 days ago too. took to mechanic and he said he is fixing 06 sti with same problem. But he can't find a solution. He replaced O2 sensor and the code come back right away.
    The mechanic said he called subaru dealership and they said this problem is fixed by using new sensor on old model and reflashing ECU on newer model. Which is new and old the dealer refuse to say...

    So i don't know know what to do with my car either. I'm don't want to buy O2 sensor that's not gonna fix the problem...
    By the way my car is 04 WRX.

    please keep me posted of your solution, thanks!

  14. #13
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    Just an update, I replaced my A/F sensor with part from subarugenuineparts.com

    Everything working perfectly now.

    *Tip: you can lend socket from autozone for free, kragen charge $6 to lent it out.

    Also you would need 3/8 extension arm atleast 6" or so to get the job done easier.

    Good luck!

  15. #14
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    big question

    i have the code p0031 but witch is it for the one by the uppipe or were my catt was sopossed to be if you can answer thanks

  16. #15
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    Quote Originally Posted by 02wrxJdmsti View Post
    i have the code p0031 but witch is it for the one by the uppipe or were my catt was sopossed to be if you can answer thanks
    It's actually the one on header. If you take out passenger wheel out and remove the splash guard you'll see a sensor sticking out from the header. it's the one that you need to remove before taking out turbo heatshield.
    hope this helps

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