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CEL P0031 after dead battery

Discussion in '1st Gen. Tacomas (1995-2004)' started by Jay W., Jul 14, 2010.

  1. Jul 14, 2010 at 8:31 PM
    #1
    Jay W.

    Jay W. [OP] Whaaat?

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    Yesterday, I had to jump my truck off to get it started. I went ahead and had the battery replaced cause it was a few years old, and it was bad. However, after I jumped my truck off, my Check Engine light came on.. w/ the P0031 code (bank 1 sensor, O2 sensor i think).

    The CEL only came on after I jumped the truck off, its not been running rough, and I haven't tried resetting it yet.. should I go ahead and find another 02 sensor, or could the low voltage from the dead battery have something to do with it?
     
  2. Aug 6, 2010 at 7:35 PM
    #2
    TacomaByTheBeach

    TacomaByTheBeach New Member

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    I think I have a similar issue and I'm wondering if you found any resolution.

    I jump started my wife's car from my toyota tacoma and as soon as i did that my check engine light came on. The code reader indicated P2238 and P0031. I cleared both codes but P0031 keeps coming back.

    Any help is much appreciated!
     
  3. Aug 10, 2010 at 9:11 PM
    #3
    Jay W.

    Jay W. [OP] Whaaat?

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    Unfortunately, after I posted this, I went to my mechanic. He cleared the code, and it came back up a couple seconds later.. so I'm guessing the O2 sensor went bad.. I'm not sure how a dead battery and jumping it off caused it to though.

    Actually getting it fixed next week, gonna talk to him a little more about the sensor and see what would have caused that.
     
  4. Aug 11, 2010 at 10:28 AM
    #4
    shampoop

    shampoop Well-Known Member

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    pure coincidence. battery has nothing to do with your 02 sensor. if your 02 sensor goes bad, it also will NOT make your truck run poorly. you may notice your mileage go down, but it will not affect the way it runs. it only affects your fuel trim a tiny bit, and when it goes bad it just makes you run a little rich all the time.
     
  5. Aug 11, 2010 at 11:43 AM
    #5
    TacomaByTheBeach

    TacomaByTheBeach New Member

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    Jay W -Thanks for responding. Yeah, I'm going to swap out the sensor and hopefully that'll do the trick.

    shampoop - Perhaps it is purely a coincidence but I find it peculiar that two different people had the same issue immediately after jump starting the vehicle. :confused:
     
  6. Aug 11, 2010 at 4:08 PM
    #6
    shampoop

    shampoop Well-Known Member

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    did you jump start the car improperly? you actually may have just shorted the O2 sensor heater somehow. forgot about the stupid heaters. the sensor itself is probably fine. the heater is only there so you car can enter closed loop a minute or 2 faster than it would otherwise.

    at school we jumped started all kinds of toyota vehicles nearly daily because every car there had a dead battery cause they never left the parking lot. never had this happen.

    just measure the resistance of the heater in the sensor and compare it to factory specs.
     
  7. Aug 12, 2010 at 10:37 AM
    #7
    TacomaByTheBeach

    TacomaByTheBeach New Member

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    shampoop - Thanks for the follow up! I may have jump started the car improperly because it's been a while since I jumped started a car. The car I was jump starting started, but it may have shorted something in my tacoma as you indicated.

    Can you elaborate on your sensor heater theory? What would I need to replace if that is the problem? Would it still be O2 sensor 1 bank 1 (before the cat)? I noticed in the shop manual that it said I can check the resistance of the sensor to see if it is still functioning correctly. Something like 20 Ohms but I don't have the book in front of me. I was going try this last weekend but I was unable to disconnect the O2 sensor because the connection is on top of the transmission. I saw a web site that said I should remove the gear shifter boot and reach it that way. I'm going to give that a go this weekend.

    BTW: My truck is 2003 Toyota Tacoma 4x4 V6.

    Many thanks to any additional insight you have!!!
     
  8. Aug 12, 2010 at 10:58 AM
    #8
    98tacoma27

    98tacoma27 :POOPCORN: Staff Member

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  9. Aug 12, 2010 at 11:49 AM
    #9
    shampoop

    shampoop Well-Known Member

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    afr and O2 sensors are the same thing by a different name. it will probably have 4 wires. one set is for the sensor, and the other is for the heater that turns on when you first start your car so the sensor can start working faster. on older cars without the heater the sensors don't work until your exhaust heats them up enough. the code you have says the resistance in the heater part of the sensor is low, suggesting that the heating element is somehow shorted. if it were high it would suggest an open.
     
  10. Aug 13, 2010 at 10:20 AM
    #10
    TacomaByTheBeach

    TacomaByTheBeach New Member

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    98tacoma27 - Thanks for the link to do PDF with the diagnostic workflow. That will come in very handy when I start troubleshooting this!!

    shampoop - Thanks for the clarification!
     
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