Symptom Diagnosis

CAUTION: When battery is disconnected, vehicle computer may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting the battery.

Symptom checks cannot be used properly unless the problem occurs while the vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC DIAGNOSTIC PROCEDURES , SELF-DIAGNOSTICS - EXCEPT 7-SERIES or SELF DIAGNOSTICS - 7-SERIES articles were performed before diagnosing a symptom. Following symptoms are available for diagnosis:

Engine Does Not Start (Will Not Crank)
Engine Cranks, But Fails To Start
Engine Backfires
Loss Of Power
Detonation (Engine Knock)
Stalls At Idle
Engine Runs Rough (Off Idle)
Rough Or Unstable Idle
Engine Misfires All Conditions
Poor Fuel Economy
Excessive Emissions