How To Use This Article

This article is to be used only AFTER you have checked the following:

• Verify the on-car diagnostics are working by performing appropriate DIAGNOSTIC CIRCUIT CHECK chart for that system.
• Verify that the ECM and "SERVICE ENGINE SOON" light are functioning properly.
• Verify that there are no trouble codes stored, or only intermittent ones.
• Verify that the fuel control system is operating properly by performing appropriate SYSTEM PERFORMANCE CHECK chart. See appropriate TESTS W/CODES article in this section.
• Perform a careful visual inspection of all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. Not all items listed under each symptom apply to all models and systems. These procedures will normally lead you to a component system on vehicle, such as EGR, EST, TCC, etc. These are covered in component system charts. These charts are listed with a "C" before the number of the chart (C1A, for example).