Important Preliminary Checks Before Starting: Review the system operation in order to familiarize yourself with the system functions. Refer to the following:
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. |
| • | If only one lamp is inoperative, inspect and repair a poor connection or an open in the power feed or ground circuit before replacing the light bulb. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. |
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 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. |
| • | Repair 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:
