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. Refer to Scan Tool Data List .
        
    • 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 electronic options, such as lights and cellular phones.
    • Use the following tables when diagnosing a symptom concern:
      •  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
      •  Malfunction Indicator Lamp (MIL) Inoperative
      •  Malfunction Indicator Lamp (MIL) Always On
    •  If the condition cannot be isolated using the appropriate table, refer to Intermittent Conditions for further diagnosis.