Diagnostic Procedure

NOTE: SERVICE ENGINE SOON light, located in instrument cluster, is referred to as the MIL.

NOTE: ALWAYS clear codes, confirm closed loop operation, and test drive vehicle after repairs are made. Ensure MIL does not illuminate.

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

Ensure all engine systems not related to computer are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Perform malfunction indicator light check before retrieving codes. See MALFUNCTION INDICATOR LIGHT (MIL) CHECK under POWERTRAIN OBD SYSTEM CHECK.
Retrieve any codes that may be present. If codes were displayed, perform appropriate DTC test under DIAGNOSTIC TROUBLE CODES . If codes were not displayed, and a driveability problem or intermittent problem exists, go to TESTS W/O CODES article.