Diagnostic Procedure

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

1. Perform visual inspection. Most driveability problems in the engine control system result from faulty wiring, poor electrical connections or leaking air and vacuum hose connections. To avoid unnecessary component testing, perform a visual inspection before beginning self-diagnostic tests.
2. Ensure all mechanical engine systems other than computerized systems (i.e., compression, ignition, etc.) are operating properly. DO NOT proceed with testing unless all other problems have been repaired. If Malfunction Indicator Light (MIL) is on, see RETRIEVING DIAGNOSTIC TROUBLE CODES . If DTCs are stored in memory, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
3. After repairs have been completed, clear DTC(s). See CLEARING DIAGNOSTIC TROUBLE CODES . Recheck system and verify repair is complete.