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 ON.

The BCM detects a short to voltage on the headlamp high beam relay control circuit.

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

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the High Beams ON with a scan tool. The High Beam Relay Command parameter should display On and the high beam headlamps should illuminate.

1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 16 and B+.

⇒	If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.

3. Install a 10A fused jumper wire between the control circuit terminal 16 and ground. The high beam headlamps should illuminate.

⇒	If the high beam headlamps do not illuminate, test the control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the underhood fuse block.

4. If all circuits test normal, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.