Preliminary Diagnostic Procedure

NOTE: The following diagnostic procedure requires use of a scan tool. See SPECIAL TOOLS (DIAGNOSTIC) .

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

Verify customer complaint. Using scan tool, obtain and record DTC and freeze frame data. Erase DTCs if present. See MALFUNCTION INDICATOR LIGHT (MIL) RESET PROCEDURE . Perform a visual inspection and ensure all engine systems not related to computer are operating properly. DO NOT proceed with diagnosis unless all other problems have been repaired.
Using scan tool, attempt to retrieve DTCs once more. If DTC(s) are present, perform appropriate diagnostic test. See DIAGNOSTIC TESTS in TESTS W/CODES article. If DTC(s) are not present, and a driveability problem or intermittent problem is present, go to TESTS W/O CODES article.

NOTE: ALWAYS erase DTCs, confirm closed loop operation, and test drive vehicle after repairs are completed. Ensure MIL DOES NOT illuminate.