P0171 Chevrolet - Avalanche 2003 code still on, now what?

Question

We have a Po171 bank 1 code appearing on our 2003 avalanche. We have replaced air filter, o2 sensors, MAF sensor, intake manifold gaskets, PCV valve and still get this code. Sprayed looking for air leaks and there were none detected.

Answer 1

P0171 Fuel system lean Bank 1

What some of the cause of P0171 are ,fuel injector,mechanical problem,vacuum leaks,low fuel pressure, plugged exhaust. When P0171 appears it is usually with P0174 (lean bank 2) and a misfire code sometimes P0300. You can swap the 02 sensor and see if the lean bank moves to the 2nd bank, You may also need to check for exhaust back pressure,which your year make a model are sensitive to plugging,