GM Service Manual Online
For 1990-2009 cars only

Important Preliminary Checks Before Starting

Perform the Diagnostic System Check - Engine Controls before using the symptom tables. Verify that all of the following conditions are true:

    • The engine control module (ECM) and the malfunction indicator lamp (MIL) are operating correctly.
    • There are no diagnostic trouble codes (DTCs) stored.
    • The scan tool data is within the normal operating range.
        
    • Verify the customer concern and locate the correct symptom listed below. Inspect items indicated under that symptom.
    • Several of the symptom procedures direct the technician to perform a visual/physical inspection. This important step can lead the technician to the cause of the problem without further checks and can save valuable time.
    • Verify the correct installation and operation of after-market electronic options.
  1. Use the following tables when diagnosing a symptom concern:
  2. •  Hard Start
    •  Surges/Chuggles
    •  Lack of Power, Sluggishness, or Sponginess
    •  Detonation/Spark Knock
    •  Hesitation, Sag, Stumble
    •  Cuts Out, Misses
    •  Poor Fuel Economy
    •  Rough, Unstable, or Incorrect Idle and Stalling
    •  Dieseling, Run-On
    •  Backfire
    •  Engine Cranks But Does Not Run
  3. If the condition cannot be isolated using the appropriate table, refer to Intermittent Conditions for further diagnosis.