Visual Inspection

Perform a comprehensive visual inspection of underhood components. Check ground connections located on intake manifold, ground cable between engine and vehicle body and that battery cables are clean and tight. See ENGINE PERFORMANCE wiring diagrams in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

Check vacuum hoses for breakage and blockage. Check electrical wiring and harness connectors for damage and corrosion. Repair as necessary. Ensure all engine systems not related to ECM are operating properly.

Check for any Technical Service Bulletins (TSBs) that may apply. DO NOT proceed with testing unless all engine problems not related to ECM have been repaired.