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:

    â€¢ The engine control module (ECM) and the malfunction indicator lamp (MIL) are operating correctly.
    â€¢ There are no diagnostic trouble codes (DTCs) stored.
    â€¢ The scan tool data is within the normal operating range. Refer to Scan Tool Data List .
        
    â€¢ Verify the customer concern and locate the correct symptom listed below. Inspect items indicated under that symptom.
    â€¢ 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.
    â€¢ Verify the correct installation and operation of electronic options, such as lights and cellular phones.
    â€¢ Use the following tables when diagnosing a symptom concern:
      â€¢  Hard Start
      â€¢  Surges/Chuggles
      â€¢  Lack of Power, Sluggishness, or Sponginess
      â€¢  Detonation/Spark Knock
      â€¢  Hesitation, Sag, Stumble
      â€¢  Cuts Out, Misses
      â€¢  Poor Fuel Economy
      â€¢  Rough, Unstable, or Incorrect Idle and Stalling
      â€¢  Dieseling, Run-On
      â€¢  Backfire
      â€¢  Malfunction Indicator Lamp (MIL) Inoperative
      â€¢  Malfunction Indicator Lamp (MIL) Always On
    â€¢  If the condition cannot be isolated using the appropriate table, refer to Intermittent Conditions for further diagnosis.