P0171 Buick -

Question

Po171 on buick regal we change bank 1 and 2 sensors, mass air flow, air buck pcv value, air hose and fluid regular and the engine still come up and it will not by emission testing for the state of Illinois

Answer 1

Intake leaks are very common on this car, low and upper intake gaskets will have air leaks, so that is something to check/replace.