P0131 Code

[angelpalomino]

I have a 2017 mustang GT with lth, pmas intake, gen 3 intake manifold, 47lb injectors and tuned on e85. A few weeks ago i noticed my check engine light come on and my afr was stuck on 9.8 no matter what.

I connected my scanner and saw code P0131 (O2 sensor circuit low voltage bank 1 sensor 1). I replaced the O2 sensor, i’ve cleaned the MAF and checked for any exhaust/vacuum leaks and everything looks good, I even tried erasing the code but unfortunately it still came back and my afr is still stuck on 9.8. Would love to hear if anyone’s had this problem before and some ways to fix it. Thank you in advance!

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[Garfy]

Have you looked at the voltage reading for that sensor? I believe it's an AFR sensor so it should be in the 3V range and what are your STFT1 and LTFT1? If you check continuity of the wires from the sensor back to the PCM and they're good (no opens or shorts), it could be a PCM fault.

 

[angelpalomino]

I just checked and my LTFT1 is at 1.0
My STFT1 is at 0.88

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