P2251 O2 sensor
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  1. #1
    chef 4 life bdiggy can identify a wrench bdiggy's Avatar
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    Default P2251 O2 sensor

    Went to auto zone to get the check engine light checked and this was the code. They said may be something loose or unplugged. Anyone have an idea what I should look for? Not even sure where the O2 sensor is. Any help would be appreciated.

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  3. #2
    EXD Pro Member 04 elantra cvvt has not yet proved knowledgeable 04 elantra cvvt's Avatar
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    Default Re: P2251 O2 sensor

    First off... Get a second opinion from someone that actually knows how to read the scan tool. The guys at AZ are not very well versed in the fine art of vehicle scanning. And, there are two sensors on the vehicle. One is at the bottom of the exhaust manifold, the other is under the car. But, please, take the car to someone that knows what the heck they are doing.

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    With Odin on our side... bfgoedeke has not yet proved knowledgeable bfgoedeke's Avatar
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    Default Re: P2251 O2 sensor

    According to the factory manual:

    P2251 - Linear O2 sensor reference ground circuit/open (bank1, sensor 1)
    (this is the front sensor)

    Disconnect ECM plug and front O2 sensor plug.
    Measure resistance:
    1 - O2 term 1 and ECM term. 41.
    2 - O2 term. 2 and ECM term. 53.
    3 - O2 term. 3 and ECM term. 40.
    4 - O2 term. 4 and ECM term. 19.

    Resistance should be below 1 ohm. If not, you have a short in the harness. If it all checks out, remove front O2 sensor and check to see if it is contaminated, deteriorated, of damaged. This is out of the factory book. Also, you didn't indicate how much mileage you got on the vehicle. It is recommended that the O2 sensor be changed after 80 - 90,000 miles. I hope this helps. Good Luck...
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    chef 4 life bdiggy can identify a wrench bdiggy's Avatar
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    Default Re: P2251 O2 sensor

    Thanks guys. Car only has 36000 on it. The wierd thing was the light went off when I filled the gas tank and came back on after about 40 miles. Auto Zone reset it so if it comes back on it looks like i'm off to the dealership. Just trying to avoid them having my car all day for something that takes, at tops, an hour to fix!

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    With Odin on our side... bfgoedeke has not yet proved knowledgeable bfgoedeke's Avatar
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    Default Re: P2251 O2 sensor

    I almost forgot, if the idiot didn't read the code correctly. You will get a code for a bad / malfunctioning purge valve if;

    1 - your gas cap is not properly tightened, or (this warning is posted inside the gas filler door)

    2 - the gas cap is no good.

    For a couple of bucks, replace the cap. I had this problem and it was intermittant. I replaced the cap and within 10-15 mins. of driving the light went off. I had about 36,000 miles on the car when it happened. Go figure....Good luck...
    17" x 7" ADR Phantom rims with Falken Ziex 512's
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    PSC rear 20mm sway bar
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    EXD Pro Member 04 elantra cvvt has not yet proved knowledgeable 04 elantra cvvt's Avatar
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    Default Re: P2251 O2 sensor

    I would suspect the 1st option. It is all too common. I see this on a regular basis around here.

  8. #7
    chef 4 life bdiggy can identify a wrench bdiggy's Avatar
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    Default Re: P2251 O2 sensor

    I thought maybe it was the gas cap too, but the first attempt did nothing and the light only went off after filling the car. Aside from that, I stood right there and looked at the code when it came up on the tester. It was definitley P2251.

  9. #8
    Player to be named later Doohickie has picked up a wrench Doohickie's Avatar
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    Default Re: P2251 O2 sensor

    Gas cap will not fix P2251; the code you get for that is P045x (where x= 4, 5, 9 maybe, etc.)
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