For 1990-2009 cars

Important Preliminary Checks Before Starting:

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

• | There are no DTCs set.

• | The body control module (BCM) can communicate via the serial data link.

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

• | Headlights Circuit Description

• | Headlights/Daytime Running Lights (DRL) Circuit Description

• | Fog Lights Circuit Description

• | Exterior Lights Circuit Description

• | Backup Lamp Circuit Description

• | Interior Lights Circuit Description

• | Interior Lights Dimming Circuit Description

### Visual/Physical Inspection

Several of the symptom procedures ask for a careful visual/physical check. This step is extremely important-it could lead to correcting a problem without further checks and can save valuable time. These checks include the following:

• | Inspect for aftermarket devices which could affect the operation of the Lighting System. Refer to Checking Aftermarket Accessories in Wiring Systems.

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

### Intermittent

Important: Check for proper installation of electrical components if an intermittent condition exists. Inspect for aftermarket theft deterrent devices, lights and cellular phones. Ensure that no aftermarket equipment is connected to the class 2 circuit. If you can not locate an intermittent condition, a cellular phone signal may cause the condition. Faulty electrical connections or wiring may also be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Important: The problem may or may not turn on the SERVICE VEHICLE SOON indicator or store a DTC. Do not use the symptom tables to diagnose intermittent conditions. The malfunction must be present in order to locate the problem.

Poor electrical connections or wiring cause most intermittent conditions. Perform a careful visual/physical check for the following conditions:

• | Poor mating of the connector halves or a terminal not fully seated in the connector body (backed out).

• | An improperly formed or damaged terminal.

• | Reform or replace connector terminals in the problem circuit in order to insure proper contact tension.

• | Poor terminal to wire connection requires removing the terminal from the connector body in order to perform the check.

Road test the vehicle with a digital multimeter (DMM) J 39200 connected to the suspected circuit. An abnormal voltage when the malfunction occurs is a good indication that there is a malfunction in the circuit being monitored.

Use a Scan Tool in order to help detect intermittent conditions. The scan tool has several features that can be used to locate an intermittent condition. The snapshot feature can capture and store data parameters within the scan tool when the malfunction occurs. This information can then be reviewed in order to see what caused the malfunction.

### Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose a symptom that does not set a DTC:

• | Backup Lamps Always On

• | Backup Lamps Inoperative

• | Backup Lamp Inoperative - One Lamp

• | Courtesy or Dome Lamps Always On

• | Courtesy or Dome Lamps Inoperative

• | Fog Lamps Always On

• | Fog Lamps Inoperative - All

• | Fog Lamps Inoperative - One

• | Fog Lamp Indicator Inoperative

• | Hazard Lamps Inoperative

• | Headlamps Inoperative - Low Beams

• | Headlamps Inoperative - High Beams

• | Headlamps Inoperative in Low Light Conditions

• | High Beam Indicator Always On

• | High Beam Indicator Inoperative

• | Instrument Panel Compartment Lamp Inoperative

• | Rear Compartment Lamp Inoperative

• | Instrument Panel Lamps Always On

• | Instrument Panel Lamps Inoperative

• | Park Lamps Inoperative

• | Park Lamps Inoperative in Low Light Conditions

• | Park Lamps Remain On in Daylight Conditions

• | Turn Signal Lamps Inoperative - Hazard Lamps Operate

• | Turn Signal Lamps Inoperative - Left or Right Side

• | Turn Signal Indicators Inoperative - Left Side

• | Turn Signal Indicators Inoperative - Right Side