For 1990-2009 cars

Important: The following steps must be completed before using a symptom table.

• | Perform the Diagnostic System Check - Vehicle before using a symptom table in order to verify that all of the following are true:

- | There are no DTCs set.

- | The control modules can communicate via the GMLAN serial data circuit.

• | Review the system description and operation in order to familiarize yourself with the system functions. Refer to the following:

- | Exterior Lighting Systems Description and Operation

- | Interior Lighting Systems Description and Operation

### Visual/Physical Inspection

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

• | Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

### Intermittent

Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, 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:

• | Backup Lamps Always On

• | Backup Lamps Inoperative

• | Repeater Lamps Inoperative

• | Courtesy Lamps Always On

• | Courtesy Lamps Inoperative

• | Fog Lamp Indicator Always On

• | Fog Lamp Indicator Inoperative

• | Rear Fog Lamp Indicator Always On

• | Rear Fog Lamp Indicator Inoperative

• | Fog Lamps Always On

• | Fog Lamps Inoperative

• | Rear Fog Lamps Always On

• | Rear Fog Lamps Inoperative

• | Hazard Lamps Always On

• | Hazard Lamps Inoperative

• | Headlamp Low or High Beams Always On

• | Headlamps Inoperative - High Beams

• | Headlamps Inoperative - Low Beams

• | Headlamps Flash to Pass Inoperative

• | High Beam Indicator Always On

• | High Beam Indicator Inoperative

• | Illuminated Entry Lamps Inoperative

• | Interior Backlighting Does Not Dim

• | Interior Backlighting Inoperative

• | Instrument Panel Compartment Lamp Inoperative

• | License Lamps Inoperative

• | Lights On Indicator Always On

• | Lights On Indicator Inoperative

• | Park Lamps Always On

• | Park Lamps Inoperative

• | Reading Lamp Inoperative

• | Rear Compartment Lamp Always On

• | Rear Compartment Lamp Inoperative

• | Repeater Lamps Inoperative

• | Stop Lamps Always On

• | Stop Lamps Inoperative

• | Turn Signal Lamps and/or Indicators Always On or Flashing

• | Turn Signal Lamps and/or Indicators Inoperative

• | Twilight Sentinel Inoperative

• | Vanity Mirror Lamp Always On

• | Vanity Mirror Lamp Inoperative