P0031 Cel
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This is a discussion on P0031 Cel within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Hey guys, I haven't been on the site in a while (starting my own business is takin all my time) ...

  1. #1
    Registered User aem421's Avatar
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    Unhappy P0031 Cel

    Hey guys,

    I haven't been on the site in a while (starting my own business is takin all my time) but I finally had my mechanic pull the CEL code for me and it was P0031 - Front oxygen (A/F) sensor heater circuit low input. I have the 1/2 watt resistor mod in place for the uppipe and the Pony Express MIL eliminator mod installed also. Any ideas as to why I'm still getting this CEL?

    I'm getting COBB to reflash my ECU anyway, so it might not even matter, but I was wondering what could be causing this.

    Any help is always appreciated. Thanks.
    '02 WRX/STi

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  3. #2
    Registered User CKxx's Avatar
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    I dont beleive that that code is related to either sensor you are tricking w/the resistors, but is refering to the O2 sensor in the passenger side manifold. Im not sure what to do about it though. sorry.
    I created my avatar.

  4. #3
    Registered User BoostedBoxer's Avatar
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    CKxx is correct. It is that sensor and the heater circuit is what "warms" up the sensor so it can work at its optimal range. Reset the light, and drive again. If it (po0031) comes on again, replace the sensor.
    My Car is 100% STOCK!
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    Originally posted by platano
    At 14???
    shoot , I'd hit it at current age, on roof of the car, with cousin driving , neighbor and town priest in the back seat, and that kid from "N.Korea" riding shotgun.

  5. #4
    Registered User ebr0t's Avatar
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    P0031 Front oxygen (A/F) sensor heater circuit low input
    Quote Originally Posted by DTR rex

    Peter North > *

  6. #5
    Registered User aem421's Avatar
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    To reset the light, I'm assuming you mean to disconnect the battery and reset the ECU. I'll give that a try again. Do you think the sensor got damaged when I had the exhaust installed or do you think it just may need cleaned? If I do need to replace it, anyone know where a good place is to get one and how hard is it to install. Thanks guys.
    '02 WRX/STi

  7. #6
    Registered User BoostedBoxer's Avatar
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    1.it is in the manifold, were they off for some reason
    2.get it at subaru, it is easy to replace if you have an 02 sensor socket (10.00 at local auto parts store)
    My Car is 100% STOCK!
    Pics

    Originally posted by platano
    At 14???
    shoot , I'd hit it at current age, on roof of the car, with cousin driving , neighbor and town priest in the back seat, and that kid from "N.Korea" riding shotgun.

  8. #7
    Registered User tubbytreats's Avatar
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    What was the solution to your problem? Did replacing the O2 sensor do the trick? I have the same P0031 CEL and I have an aftermarket ScoobySport uppipe and downpipe. I'm thinking that either the wiring to the O2 sensor has gone bad (or melted) and that the sensor itself is fine.

    I will be checking the resistance of the O2 sensor with a multimeter and will post my results back. If it is a bad O2 sensor, I should have no problems swapping it out with a rented O2 sensor socket from Advanced Auto Parts (free if you return it within a week)!

    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)

  9. #8
    Registered User aem421's Avatar
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    tubbytreats,

    Yes, after replacing the front O2 sensor, my CEL has gone out. The problem was fixed. No more CEL
    '02 WRX/STi

  10. #9
    Registered User tubbytreats's Avatar
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    I rented an O2 sensor socket from AutoZone last night and tried jiggling the wires on the O2 sensor, removing and re-inserting and all. Nothing seemed to get rid of that CEL, even though I reset my ECU with the AccessPORT several times and started the car up. The CEL would stay out for maybe 10 seconds and then turn on with a solid light.

    How much did you pay for your O2 sensor, and did you have the dealer replace it? I priced some out really quick and they were $160. Is that normal, or am I getting ripped off??

    Comments are always welcome.

    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)

  11. #10
    Registered User aem421's Avatar
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    Yeah, that's exactly what mine did. It would go off for about 10 seconds and then come right back on. I didn't feel like foolin with it so I had the dealer replace it. I have a good relationship there with the mechanic so he cut me a break. The price you got is very good. The dealership price is around $250. Good luck.
    '02 WRX/STi

  12. #11
    Registered User tubbytreats's Avatar
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    aem421,

    Sorry to be such a bother, but I looked on http://www.SubaruParts.com and they have a few different O2 sensor part #'s listed. I'm trying to determine which one would be the proper one for my 2002 Subaru WRX sedan. They are between $90 and $114 and would be MUCH cheaper than the dealership I'm sure!!

    Is there a way for you to find which part number you have for your own O2 sensor? My searched here on ClubWRX.net and Nasioc.com are very unfruitful to find the proper part number.

    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)

  13. #12
    Registered User aem421's Avatar
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    I'm not sure off the top of my head. When I get home tonight I'll look at the invoice and check the part number. I'll let you know. If not, you can always go to the dealership and get them to give you the part number for the "front O2 sensor" that comes off the passenger side exhaust manifold.
    '02 WRX/STi

  14. #13
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    Wow, funny for this thread to pop up now, i was pulling codes last week with my homemade scan tool and figured it was a bug in my software because i thought there were no codes below P0100. Odd i had this and a P0420 (was catless at the time), but just reset the codes and went back to stock exhaust but kept the catless uppipe with stock heat shields on it. Passed smog just fine and that CEL never came back. The only time ive touched the front 02 sensor was when installing the catless uppipe, but that was a long time ago. Wonder what might have caused that, oh well it hasn't come back in 200 miles yet so we'll see in another 1000 miles or so.
    2003 WR Blue WRX - Godspeed Up/Down pipe - Prodrive Axel Back - MBC (14.75psi in 3rd) - 220 WHP on Dynopak (93oct)

  15. #14
    Registered User tubbytreats's Avatar
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    Quote Originally Posted by aem421
    I'm not sure off the top of my head. When I get home tonight I'll look at the invoice and check the part number. I'll let you know. If not, you can always go to the dealership and get them to give you the part number for the "front O2 sensor" that comes off the passenger side exhaust manifold.
    Thanks a ton! Muchly appreciated!!

    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)

  16. #15
    Registered User aem421's Avatar
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    OK...I found the part number. It's 22641AA042. www.subaruparts.com has if for $152.36. That's what they replaced on my car to fix the CEL. Good luck man.
    '02 WRX/STi

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