GM Service Manual Online
For 1990-2009 cars only

Important Preliminary Inspections Before Beginning

Perform Diagnostic System Check - Engine Controls before using the symptom tables, and verify that all of the following are true:

    â€¢ The control module and malfunction indicator lamp (MIL) are operating correctly.
    â€¢ There are no 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. Inspect the items indicated under that symptom.
    â€¢ Several of the symptom procedures ask for a careful visual and physical inspection. This step is extremely important. The visual and physical inspection can lead to correcting a problem without further inspections, and can save valuable time.
    â€¢ Inspect for improper installation of electrical components if an intermittent condition exists. Inspect for aftermarket theft deterrent devices, lights, and cellular phones. If you can not locate an intermittent condition, a cellular phone communication signal may cause the condition.
    â€¢ If the intermittent condition exists as a start and then stall, test for DTCs relating to the vehicle theft deterrent system.

Use the following tables when diagnosing a symptom complaint:

    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€¢  Poor Fuel Fill Quality
    â€¢  Rough, Unstable, or Incorrect Idle and Stalling
    â€¢  Dieseling, Run-On
    â€¢  Backfire