Important: The following steps must be completed before doing the Symptom tables.
- Perform the 
Diagnostic System Check - Vehicle
 .
 
| •  | The control modules can communicate via the serial data link. | 
 
- Review the system operation in order to familiarize yourself with the system functions. Refer to the following:
 
Visual/Physical Inspection
|     •  | Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom. | 
 
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to 
Testing for Intermittent Conditions and Poor Connections
 .
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom: