Important Preliminary Inspections Before Beginning

Perform Diagnostic System Check - Vehicle in Vehicle DTC Information before using the symptom tables, and verify that all of the following are true:

• The control module and malfunction indicator lamp (MIL) are operating correctly.
• There are no 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. Inspect the items indicated under that symptom.
• 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.
• 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.
• 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:

• Hard Start 
• Surges/Chuggles 
• Lack of Power, Sluggishness, or Sponginess 
• Detonation/Spark Knock 
• Hesitation, Sag, Stumble 
• Cuts Out, Misses 
• Poor Fuel Economy 
• Poor Fuel Fill Quality 
• Rough, Unstable, or Incorrect Idle and Stalling 
• Dieseling, Run-On 
• Backfire