Diagnosis Of Computerized Engine Control System Should Be Performed In The Following Order:
- Ensure all 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 MIL is on, see RETRIEVING CODES. For diagnosing hard codes, see DTC IDENTIFICATION table to determine the probable cause of malfunction. See DIAGNOSTIC TESTS for test procedures corresponding to fault codes.
- For diagnosing intermittent codes, proceed to INTERMITTENTS in TESTS W/O CODES article. Inspect condition of system harness by performing recommended voltage or continuity checks. See WIRING DIAGRAMS article for additional information on specific circuit configuration. Inspect condition of individual component. Repair or replace component as needed.
- Recheck system operation after repair is completed. If DTC still exists, substitute known-good ECM, then retest system. Verify system is repaired. After repairs have been completed, clear DTC(s). See CLEARING CODES.