B+ is applied at all times to the headlamp high beam relay. When the headlmap dimmer switch is placed in either the flash to pass (FTP) or HIGH position, ground is applied through the signal circuits to the body control module (BCM). The BCM then applies a ground to the headlamp high beam relay control circuit. This energizes the relay and applies voltage through the HI BEAM fuses to both left and right headlamp assembly.

The ignition is ON. The high beam headlamps are commanded ON.

The BCM detects a short to ground or an open/high resistance on the headlamp high beam relay control circuit while trying to energize the relay.

The BCM disables the headlamp high beam relay control 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 and OFF with a scan tool. The headlamp high beams should turn ON and OFF when changing between the commanded states.

1. Ignition OFF, disconnect the HI BEAM relay.
2. Connect a test lamp between the control circuit terminal E20 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, test or replace the HI BEAM relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming