Important Preliminary Checks Before Starting
- Perform
Diagnostic System Check - Vehicle, before using the symptom tables in order to verify that all of the following are true:
| • | The body control module (BCM) can communicate via the serial data link. |
- Review the system operation in order to familiarize yourself with the system functions:
Visual/Physical Inspection
Several of the symptom procedures ask for a careful visual/physical check. This step is extremely important, it could lead to correcting a problem without further checks and can save valuable time. These checks include the following:
| • | Inspect the easily accessible or visible system components and harness connectors for obvious damage or conditions which could cause the symptom. |
Intermittent
Important:
| • | Check for proper installation of electrical components if an intermittent condition exists. Inspect for aftermarket theft deterrent devices, lights and cellular phones. Ensure that no aftermarket equipment is connected to the class 2 circuit.
If you can not locate an intermittent condition, a cellular phone signal may cause the condition. Faulty electrical connections or wiring may also be the cause of intermittent conditions. Refer to
Testing for Intermittent Conditions and Poor Connections. |
| • | The problem may or may not turn on the SERVICE VEHICLE SOON indicator or store a DTC. Do not use the symptom tables to diagnose intermittent conditions. The malfunction must be present in order to locate the problem. |
Poor electrical connections or wiring cause most intermittent conditions. Perform a careful visual/physical check for the following conditions:
| • | Poor mating of the connector halves or a terminal not fully seated in the connector body |
| • | An improperly formed or damaged terminal |
| • | Reform or replace connector terminals in the problem circuit in order to insure proper contact tension. |
| • | Poor terminal to wire connection requires removing the terminal from the connector body in order to perform the check. |
Use a scan tool in order to help detect intermittent conditions. The scan tool has several features that can be used to locate an intermittent condition. The snapshot feature can capture and store data parameters within the scan tool when the malfunction
occurs. This information can then be reviewed in order to see what caused the malfunction.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:
