For 1990-2009 cars

Important: The following steps must be completed before using the symptom tables.

1. Perform the Diagnostic System Check - Vehicle , check and verify the following conditions are met:

• | No DTCs are set.

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

2. Review the system operation in order to familiarize yourself with the system functions. Refer to:

• | Data Link Communications Description and Operation

• | Body Control System Description and Operation

• | Retained Accessory Power (RAP) Description and Operation

### Visual/Physical Inspection

• | Inspect for aftermarket devices which could affect the operation of the systems. Refer to Checking Aftermarket Accessories .

• | 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:

• | Scan Tool Does Not Power Up

• | Scan Tool Does Not Communicate with High Speed GMLAN Device

• | Scan Tool Does Not Communicate with Low Speed GMLAN Device

• | Retained Accessory Power (RAP) On After Timeout

• | Retained Accessory Power (RAP) Inoperative