- Symptoms - Engine Controls

Symptoms - Computers and Control Systems

Important Preliminary Inspections Before Beginning

Perform Diagnostic Trouble Code (DTC) List - Vehicle 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. 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. Diagnostic Trouble Code Descriptions

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