Diagnostic Starting Point - Engine Controls

WARNING: This page is about a different car, the 2003 GMC Sonoma and 2003 Chevrolet S10 Pickup. 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 - 2.2L SONOMA & S10 PICKUP article. Doing so will help identify proper system or component to check in SYSTEM & COMPONENT TESTING - 2.2L SONOMA & S10 PICKUP article.
After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.