Symptom Diagnosis
Verify customer complaint and locate correct symptom. Check items, systems and components listed under symptom grouping. Symptom groupings cover several engines and contain possible causes for each symptom. Procedures listed do not have to be done in consecutive order. If scan tool does not indicate a problem, proceed with diagnosis in a logical order. Start with easiest check or most likely cause first.
To reduce diagnostic time, ensure basic diagnostic procedures in the BASIC TESTING article and self-diagnostic procedures in the TESTS W/CODES articles were performed before diagnosing a symptom. Symptoms available for diagnosis include:
- Hard Starting (Cranks Okay)
- Engine Surges And/Or Chuggles
- Lack Of Power, Sluggish Or Spongy
- Detonation/Spark Knock
- Hesitation, Sag Or Stumble
- Cuts Out, Misses
- Poor Fuel Economy
- Rough, Unstable Or Incorrect Idle, Stalling
- Engine Diesels, Runs On
- Engine Backfires
NOTE:
Systems and components listed under each symptom may not be applicable to all models. Refer to underhood information labels and appropriate wiring diagrams. See appropriate wiring diagrams in WIRING DIAGRAMS
article.