Diagnostic Starting Point - Engine Controls

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Pontiac Grand Prix, 2003 Pontiac Bonneville, 2003 Chevrolet Monte Carlo, 2003 Chevrolet Impala, and 2003 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.

Diagnosis of computerized engine control system should be performed in the following order:

Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Diagnostic system check must be performed before using specific DTC testing procedure. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article. Doing so will help identify proper system or component to check in SYSTEM & COMPONENT TESTING - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.