Diagnostic Aids

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.

Fuel contamination, such as water and alcohol, will affect the fuel trim.
The system will go rich if the injectors are supplying too much fuel.
Review the Failure Records using a scan tool. If intermittent condition is suspected, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.