How To Use This Section

This portion of article is used only AFTER you have checked the following:

• Verify on-vehicle diagnostics work (if equipped). Perform DIAGNOSTIC CIRCUIT CHECK from BASIC TESTING article.
• Verify ECM and SERVICE ENGINE SOON light function properly.
• Verify no trouble codes stored, or only intermittent ones.
• Verify fuel control system operates properly. Perform FIELD SERVICE MODE CHECK in BASIC TESTING article.
• Perform fuel system pressure test.
• Visually inspection all systems.

After performing all checks performed, verify customer complaint and locate correct symptom among those listed in this article. Not all items listed under each symptom apply to all models and systems. These procedures will normally recommend testing of a system or component on vehicle, such as EGR, EST, TCC, etc. These are covered in the SYSTEM/COMP TESTS article.