Headlamp Switch: Testing and Inspection

For circuit descriptions and diagrams, refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, REFER TO ELECTRICAL, RESTRAINTS BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

1. Disconnect and isolate the battery negative cable. Remove the headlamp switch from the instrument panel. (Refer to HEADLAMP SWITCH - REMOVAL Service and Repair) for the procedures. Unplug the headlamp switch wire harness connectors. Check for continuity between the left door jamb switch sense circuit cavity of the headlamp switch wire harness connector and a good ground. There should be continuity with the driver door open, and no continuity with the driver door closed.
If OK, go to Step 2.
If not OK, repair the circuit to the driver door jamb switch as required.

2. Remove the Central Timer Module (CTM) from its mounting bracket to access the CTM wire harness connectors. (Refer to BODY CONTROL/ CENTRAL TIMER MODULE - REMOVAL Body Control Module) for the procedures. Unplug the 14-way CTM wire harness connector. Remove the key from the ignition lock cylinder.
Check for continuity between the key-in ignition switch sense circuit cavity of the 14-way CTM wire harness connector and a good ground. There should be no continuity.
If OK, go to Step 3.
If not OK, repair the short circuit as required.

3. Check for continuity between the key-in ignition switch sense circuit cavities of the 14-way CTM wire harness connector and the headlamp switch wire harness connector. There should be continuity.
If OK, go to Step 4.
If not OK, repair the open circuit as required.

4. Check for continuity between the left front door jamb switch sense circuit terminal and the key-in ignition switch sense circuit terminal of the headlamp switch. There should be no continuity with the switch in the OFF position, and continuity with the switch in the park or head lamps ON position.
If OK, (Refer to BODY CONTROL/CENTRAL TIMER MODULE - DIAGNOSIS AND TESTING Body Control Module).
If not OK, replace the faulty headlamp switch.