Important: For the rear window defogger system, the following steps must be performed before using the symptom tables.
- Perform the 
Diagnostic System Check - Vehicle
 before using the symptom tables in order to verify that all of the following are true: 
 
| •  | The control modules can communicate via the serial data link. | 
 
- Review the power window system operation or rear window defogger system operation in order to familiarize yourself with the system functions. Refer to 
Rear Window Defogger Description and Operation
 .
 
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: