Headlamps Inoperative - High Beams

HEADLAMPS INOPERATIVE - HIGH 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. When the headlamp high beam relay coil is energized, current flows through the LH HIGH and the RH HIGH fuses to the high 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

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

High Beam Headlamps Inoperative - Both
1. Ignition OFF, disconnect the high beam relay.
2. Connect a 10-amp fused jumper between the high beam relay voltage supply circuit and the high beam headlamps switched voltage supply circuit at the high beam relay terminals. The high beam headlamps should illuminate.
- If the high beam headlamps do not illuminate, repair the high beam headlamp 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 high beam relay coil side voltage supply circuit and the headlamp high beam relay control circuit at the high beam relay terminals.
4. Ignition ON, install a scan tool and command the high beam headlamps ON. The test lamp should illuminate.
- If the test lamp does not illuminate, repair the headlamp high beam relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. Connect the high beam relay.
6. With a scan tool command the high beam headlamps ON. The high beam headlamps should illuminate.
- If the high beam headlamps do not illuminate, test or replace the high beam relay.
7. Ignition OFF, disconnect the C2 harness connector at the turn signal/multifunction switch.
8. Connect a 3-amp fused jumper between the headlamp dimmer switch high beam signal circuit and the headlamp switch signal circuit.
9. Ignition ON, verify that the high beam headlamps illuminate.
- If the high beam headlamps do not illuminate, repair the headlamp dimmer switch high beam signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
10. If all circuits test normal, replace the turn signal/multifunction switch.

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)
- Control Module References for BCM replacement, setup, and programming