The high beam headlamps can be controlled by two different inputs to the body control module (BCM), the dimmer switch and the flash to pass switch. When the BCM receives a high beam headlamps ON command, it grounds the headlamp high beam relay control circuit in order to energize the high beam PCB relay. With the relay energized, battery voltage is applied through switch side of the relay, both HI BEAM fuses, and the high beam supply voltage circuits to the high beam headlamps.

The high beam headlamps must be commanded ON by the BCM.

The BCM detects a short to voltage on the low beam headlamps relay control circuit.

The BCM will deactivate the high beam PCB relay for the remainder of the ignition cycle.

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Lighting Systems Connector End Views

Connector End View Reference

Scan Tool Reference

1. Ignition OFF, disconnect the (C2) harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal 19 and B+.
3. Ignition ON, command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

4. If the circuit tests normal, replace the underhood fuse block.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.