How To Use This Section

Use this portion of article only AFTER performing these checks:

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

After performing these checks, verify customer complaint, and locate correct symptom from among those listed in this article. Not all items listed under each symptom apply to all models and systems. These procedures normally recommend testing of a system or component on vehicle, such as EGR, EST, TCC, etc. See I - SYS/COMP TESTS article for specific testing procedures.