O2 sensor responsible for P0171?

[750iClown]

Originally Posted by M_Bimmer

Well, sounds like you are back on post #82...

Seriously, I do hope to hear some good news on your issue....

I think it's actually fixed. I swapped the O2 sensor that I previously removed from bank 1 with bank 2. I then drove the car to a nearby gas station with 91 non-ethanol gas and put 12 gallons in. Ithink it could be bad gas that's been sitting in there. I drove the car for a little while, got it up to temperature. Shut it down multiple times, started it multiple times and the CEL has not returned. I'll really feel good about it tomorrow if no CEL returns. Last time I cleared faults in ISTA, the CEL reappeared very quickly. It doesn't seem to be returning this time. Fingers crossed when I do another test drive.

[750iClown]

Originally Posted by M_Bimmer

Well, sounds like you are back on post #82...

Seriously, I do hope to hear some good news on your issue....

Started it again this morning and let it sit in the garage running up to temp. Revved the engine for a bit, and no CEL. When this code/CEL popped before, it happened within seconds of starting the car after clearing faults in ISTA. The car has been running for a while now with multiple starts and drives and no CEL! I think what may have done the trick was putting 12 gallons of non-ethanol 91 octane, to be honest, but it could also be initially replacing the bank 1 precat O2 sensor. Wooooo!

Update. A few hours later this morning I drove it around neighborhood. Gunned it a few times and let me tell ya, fastest car I've ever driven holy shit! Most importantly, no CEL

[Raimo5]

Glad to see the improvements. Was the O2 sensor that you swapped new one that you bough or the old one? Also, how old was the fuel in the tank? Problems being solved by adding fuel could also indicate towards weak low pressure pump. In your case, I also wouldn't rule out water contamination.

[750iClown]

Originally Posted by Raimo5

Glad to see the improvements. Was the O2 sensor that you swapped new one that you bough or the old one? Also, how old was the fuel in the tank? Problems being solved by adding fuel could also indicate towards weak low pressure pump. In your case, I also wouldn't rule out water contamination.

Idk how old the fuel was, but I'm going to stop at nearby Autozone to grab some dry gas or Heet and add it to the tank. What I did with the O2 sensors was replace bank 1 precat O2 sensor with a brand new sensor. After I did that, the code went from P0171 to P0174. So rather than purchase another O2 sensor for bank2, I used the old one I removed from bank 1 and put that one on bank 2. I then added 12 gallons of fresh fuel. The code, knock on wood, appears to be gone.

[Raimo5]

I would advise you to replace bank 2 O2 sensor with new one as well. Old one from bank 1 has already proven to be unreliable and just because it is currently not producing errors doesn't mean that data it produces is of highest quality. I have seen many fuel regulating probes creating drivability issues while not triggering any error codes. Internal diagnostics is designed to identify anomalous deviations, but if whole signal spectrum is drifting in sync then that is impossible to identify.

[750iClown]

Originally Posted by Raimo5

I would advise you to replace bank 2 O2 sensor with new one as well. Old one from bank 1 has already proven to be unreliable and just because it is currently not producing errors doesn't mean that data it produces is of highest quality. I have seen many fuel regulating probes creating drivability issues while not triggering any error codes. Internal diagnostics is designed to identify anomalous deviations, but if whole signal spectrum is drifting in sync then that is impossible to identify.

I was doing some thinking just prior to coming back to this thread this morning. I am going to remove the brand new sensor and put the old one back and I'm going to drive it around and test for as long as is needed to see if the problem all along was bad/old gas. Because I don't think it's a coincidence that the code hasn't returned since I filled the tank w gas. If the code doesn't come back we have our answer.

[750iClown]

Originally Posted by Raimo5

I would advise you to replace bank 2 O2 sensor with new one as well. Old one from bank 1 has already proven to be unreliable and just because it is currently not producing errors doesn't mean that data it produces is of highest quality. I have seen many fuel regulating probes creating drivability issues while not triggering any error codes. Internal diagnostics is designed to identify anomalous deviations, but if whole signal spectrum is drifting in sync then that is impossible to identify.

Both old O2 sensors are back in and no code. It was the bad gas all along.

https://photos.app.goo.gl/xFEajVw9woGvCMLo9

[M_Bimmer]

750iClown very happy for you. This was sort of a long road for closure on your G12....looks like you can close this thread

[750iClown]

Originally Posted by M_Bimmer

750iClown very happy for you. This was sort of a long road for closure on your G12....looks like you can close this thread

Thanks. Yes, but in hindsight one of the first things I should have done was fill the tank with fresh gas! I'm going to sell the O2 sensor on ebay or somewhere. The vehicle and existing O2 sensors only have 18k miles on them, meaning a good 80k life left on them.