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post #1 of 8 (permalink) Old 03-06-2014, 05:56 PM Thread Starter
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CEL - Multiple Codes, Possible O2 Sensor, Not Sure. LNF

hey guys i've lurked here a while and i guess its time to post..

The other day my CEL came on and i got: P2196, P0137, P0138, P0036, P2096, P2097

I cleared the codes and was all good for a couple days
Now i just get P0141 & P0036 of which when i clear will come back.

Also with my scan tool connected, under fuel system status shows "closed loop control but fault exists"

All are related to o2 sensor so im thinking that may be the cause, although i'm not sure.

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Last edited by revnr; 03-06-2014 at 06:05 PM.
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post #2 of 8 (permalink) Old 03-08-2014, 06:27 PM Thread Starter
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So Last two times I have started the car it seems to start fine but then immediately almost stalls until it regains rpms. I'm still unsure what the problem could be.
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post #3 of 8 (permalink) Old 03-08-2014, 07:01 PM
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P2000 and up codes are not valid for a Cobalt, the other codes all lead to a bad downstream HO˛ heater. Could also be frayed wires so check wiring to second Ho˛ sensor first.

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post #4 of 8 (permalink) Old 03-08-2014, 07:54 PM Thread Starter
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Thanks I was leaning towards the downstream o2 but what had me unsure was the p2196 which says bank1 sensor1 signal biased/stuck rich, but you say the p2000 codes aren't valid. And then the closed loop with fault, the downstream o2 has no influence or drivability just monitors the cat, correct?

I'll have to check the downstream o2 and the wiring tomorrow. If I see nothing wrong would it be worth replacing?
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post #5 of 8 (permalink) Old 03-08-2014, 08:56 PM
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I have both O2 sensors for sale if you're interested. Replaced both a while back, then the problem turned out to be a blown fuse :-/

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post #6 of 8 (permalink) Old 03-09-2014, 08:29 PM Thread Starter
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So during a cold start it almost seems like it's skipping cat warmup. It's a little rough for a couple seconds and I don't here the normal sound of the intake sucking in air which is especially noticeable with the k&n Sri.

Is it possible that if the downstream o2 isn't working the car would have no idea on the status of the cat and therefor not know weather or not to go into cat warmup mode?

Originally Posted by colodude18 View Post
I have both O2 sensors for sale if you're interested. Replaced both a while back, then the problem turned out to be a blown fuse :-/
Thanks for the offer but My dad is able to get me one it need be.

Last edited by revnr; 03-09-2014 at 08:32 PM.
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post #7 of 8 (permalink) Old 03-11-2014, 01:15 AM
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Ill say this about the 02 sensors on LNFs. The front 02 sensor is what makes the rough instant fuel changes (STFTs or Short Term Fuel Trims) and the rear 02 monitors the cat as well as the fine LTFTs (Long Term Fuel Trims or cruising fuel trims). When you go WOT your rear 02 turns off completely. Now, your rear 02 also controls the cold start fuel trims to allow for the computer to effectively adjust the timing and add more fuel to properly and efficiently heat up your cat to NOT (Normal Operational Temperature).

Now with all that being said, you need to replace your rear 02. If you smell rotten eggs while your car is running, time to replace the cats, if not, hurry and reaplace that rear sensor before you kill your cats.

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post #8 of 8 (permalink) Old 03-14-2014, 03:21 PM Thread Starter
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Update - Replaced downstream O2 and all is good. Just as I expected, but thanks for the help!
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