Diagnostic Aids

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. 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, refer to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.