Symptoms - Computers and Control Systems

Symptoms - Computers and Control Systems

Important Preliminary Inspections Before Beginning

Before using this section, perform the Diagnostic System Check - Vehicle and verify all of the following conditions: Diagnostic System Check - Vehicle

* The powertrain control module (PCM) and the malfunction indicator lamp (MIL) are operating correctly. Refer to Malfunction Indicator Lamp (MIL) Inoperative. Malfunction Indicator Lamp (MIL) Inoperative
* Diagnostic trouble codes (DTCs) are not 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 table. Inspect the items indicated in that symptom table.
* Several of the symptom procedures ask for a careful visual/physical inspection. This step is extremely important, and can lead to correcting a condition without further inspections and can save valuable time.
* If the intermittent condition exists as a start and then stall, inspect for any DTCs related to the theft deterrent system. Refer to Diagnostic System Check - Vehicle. Diagnostic System Check - Vehicle
* Verify the proper installation of any of the following aftermarket accessories:

- Lights
- Cellular phone
- Remote starter system
- Aftermarket installed alarm

* Use the following tables when diagnosing a symptom concern:

- Poor Fuel Fill Quality
- 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

* If the condition cannot be isolated using the appropriate table, refer to Intermittent Conditions for further diagnosis. Intermittent Conditions