P2231 Oxygen sensor pending code

[Oli77]

I have on and off detected a P2231 code on my 2005 (non ZHP).

Because there are not that many threads out there on this code and the little bit I have found was not in our own site, I figured we and the rest of the world could benefit from the Collective Mafia Knowledge (CMK).

The code is pending and apparently indicates bank 1 sensor 1 is "shorting to heater circuit". Car has zero issues in term of performance.

3 Initial questions.

1) can I just go on for now?
2) what worst symptoms will I encounter if I do nothing.
3) should I change one or both precat sensors?

Thanks in advance for your CMK.

[ryankokesh]

As I understand it, the sensors only work when hot, so they have heater coils (I guess?) in them to get them up to temp when you start it cold.

Not sure how much of this you know already, but basically their job is to adjust the fuel:air mixture by sending feedback about the oxygen levels in the exhaust. If the engine is cold, or the sensors are not working, the computer kind of defaults to its spec ratios. This is referred to as going into "Open Loop". At this point it isn't relying on the sensors to optimize the fuel mixture. When they get up to temp, the car will go into "Closed Loop" where it's adjusting based on the O2 sensor feedback.

So it sounds like your sensors aren't warming up with the coil. I think it'll just make your car stay in open loop longer, until the sensors warm up on their own from the exhaust heat.

[Oli77]

Thanks Ryan for answering, I had forgotten about this thread.
And thanks for your explanation as I know nothing about the function of those sensors.
Occasionally, when I start the car, an alarm sounds on my UltraGuageII to let me know about the pending code.
Problem is that every minute I get an alarm so I disable it. I should try and see if driving until sensor is hot stops the alarm.

Will try that and report back.

Ultimately, this seems like I should change at least the one sensor.

[Oli77]

Driving until sensor is hot does not stop the alarm.

If its warm when I start the car, no issue.

I am tempted to keep driving for now.

[Oli77]

Code no longer pending and manifested as a solid trouble code about 24 hours after I noticed a pretty strong vibration throughout the car when idling. Feels like a cylinder is not firing and gets engine off timing.
I could be wrong. But this is the feeling I get.
The service engine soon light came on 2 seconds after my Ultra Guage identified the code.
Strange thing is that the problem only manifests at idle. Car still pulls strong.

Will take to mechanic and report.

[Oli77]

230 dollars and problem is solved with a new oxygen sensor bank 1.

[ELCID86]

One sensor? Pre-cat? I assume not a DIY at that price. Didn't want to do both?


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"ZHP is a garbage option anyway- just some cosmetic upgrades with a different cam and diff to claw back some of the performance lost fitting those hideous and heavy wheels. Any 330 with a 3.46 diff will smoke a ZHP every time. The whole Mafia thing reeks of childish behavior." - anonymous E46 fanatic

[Oli77]

No diy. Not one minute. Pay to play.
Only changed the one. It was influencing the engine so much.

[ELCID86]

No diy. Not one minute. Pay to play.
Only changed the one. It was influencing the engine so much.