Headlamps Inoperative - Low Beams

HEADLAMPS INOPERATIVE - LOW BEAMS




DIAGNOSTIC FAULT INFORMATION

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

CIRCUIT/SYSTEM DESCRIPTION
With the headlamp switch in the HEAD position, the headlamp switch headlamp ON signal circuit is grounded through the turn signal/multifunction switch at G201. In response to this input, the body control module (BCM) provides ground to either the headlamp low beam relay control circuit through the headlamp switch signal circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay coil has ground. The BCM supplies ground to the relay coil circuits, if the headlamps are necessary. The underhood fuse block supplies battery positive voltage to both relay switch circuits. When the low beam relay coil is energized, current flows through the LH LOW and the RH LOW fuses to the low beam headlamps. Ground for the left headlamp assembly is provided at G101. Ground for the right headlamp assembly is provided at G102.

CIRCUIT/SYSTEM TESTING

Low Beam Headlamps Inoperative - One
1. Ignition OFF, disconnect the inoperative low beam headlamp.
2. Connect a test lamp between the low beam headlamp voltage supply circuit and ground.
3. Ignition ON, turn ON the headlamps. The test lamp should illuminate.
- If the test lamp does not illuminate, repair the low beam headlamp voltage supply circuit for a short to ground or an open/high resistance.
4. Verify that a test lamp illuminates between the low beam headlamp voltage supply circuit and the inoperative headlamp ground circuit.
- If the test lamp does not illuminate, repair the low beam headlamp ground circuit for an open/high resistance.
5. If all circuits test normal, replace the inoperative low beam headlamp.

Low Beam Headlamps Inoperative - Both
1. Ignition OFF, disconnect the low beam relay.
2. Connect a 10-amp fused jumper between the low beam relay voltage supply circuit and the low beam headlamps switched voltage supply circuit at the low beam relay terminals. The low beam headlamps should illuminate.
- If the low beam headlamps do not illuminate, repair the low beam headlamps voltage supply circuits for a short to ground or an open/high resistance. If circuits test normal, replace the underhood fuse block.
3. Connect a test lamp between the low beam relay coil side voltage supply circuit and the headlamp low beam relay control circuit at the low beam relay terminals.
4. Ignition ON, turn ON the low beam headlamps. The test lamp should illuminate.
- If the test lamp does not illuminate, repair the headlamp low beam relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the turn signal/multifunction switch.
5. If all circuits test normal, test or replace the low beam relay.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

- Multifunction, Turn Signal Switch Replacement
- Headlamp Bulb Replacement
- Underhood Electrical Center or Junction Block Replacement
- Relay Replacement (Within an Electrical Center) Relay Replacement (Attached to Wire Harness)