P0171 GMC -

Question

Can this code be caused due to a bad welding on a newly installed flowmaster.

Answer 1

P0171 Fuel trim lean Bank 1

Yes it can, it can .

 Here is a S10 Blazer, there was a exhaust leak, and in here there still is. what happen here a P0171 is coded on top of that there is a  MAF (mass airflow ) code P0101 which is MAF circuit range /  perfromance., what this exhaust leak did was blame the MAF for poor perfromance . The fix was to replace the exhaust pipe. It took care of the P0101 and P0171, When all was done the idle was so smooth.