P0171 -Can a P0171 code be caused by poor/no downstream O2 sensors?

Question

I have the P0171 constantly. I have at times come up with the P1131 and P1132 codes as well. The upstream O2 sensor has been replaced. The MAF seems to work. Leaks have not been detected, but the muffler had some hair removed recently as it started coming out. The only code I get is the P0171 lean code recently.

Answer 1

Hi there,

The answer is yes, a poorly functioning O2 can cause the code. Also, it's possible if there is some blockage in the exhaust it's blowing the exhaust back into the engine and causing the lean mixture code.