For 1990-2009 cars

The following steps must be performed before using the symptom tables.

1. Perform the Diagnostic System Check - Defogger before using the symptom tables in order to verify that all of the following are true:

• | There are no DTCs set.

• | The control modules can communicate via the serial data link.

2. Review the 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 for aftermarket devices which could affect the operation of the rear window defogger or the automatic day-night feature of the inside rearview mirror. Refer to Checking Aftermarket Accessories in Wiring Systems.

• | 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 in Wiring Systems.

### Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

• | Rear Window Defogger Inoperative

• | Defogger Grid Lines Diagnosis