Headlamps - Halogen

NOTE:

As part of the exterior lighting fail safe feature, upon ignition ON all exterior park lamps and the headlamp low beams will illuminate regardless of the headlamp switch control knob position if the IC cannot detect an input from the headlamp switch, or if there is a loss of communication between the multi-function switch/Steering Column Control Module (SCCM) microcontroller and the BCM. Diagnose and repair those problems before attempting to repair the headlamps. In addition, the BCM will store a DTC for an open or shorted headlamp circuit.

CONDITION	POSSIBLE CAUSES	CORRECTION
HEADLAMP DOES NOT ILLUMINATE	1. Ineffective or missing bulb.	1. Test and replace headlamp bulb or unit as required.
	2. Ineffective ground circuit.	2. Test and repair open headlamp ground circuit if required.
	3. Ineffective feed circuit.	3. Test and repair open headlamp low beam or high beam feed circuit if required.
	4. Ineffective switch.	4. Test and replace the headlamp switch if required.
	5. Ineffective BCM inputs or outputs.	5. Use a diagnostic scan tool to test the BCM inputs and outputs. Refer to the appropriate diagnostic information.
HEADLAMP DOES NOT EXTINGUISH	1. Ineffective feed circuit.	1. Test and repair shorted headlamp low beam or high beam feed circuit if required.
	2. Ineffective switch.	2. Test and replace headlamp switch if required.
	3. Ineffective BCM inputs or outputs.	3. Use a diagnostic scan tool to test the BCM inputs and outputs. Refer to the appropriate diagnostic information.
HEADLAMPS ILLUMINATE WITH IGNITION ON AND HEADLAMP SWITCH OFF (FAIL-SAFE OPERATION)	1. Loss of LIN or CAN data bus communication.	1. Test and repair the LIN or CAN data bus if required. Refer to the appropriate diagnostic information.
HEADLAMPS WILL NOT SWITCH FROM HIGH TO LOW BEAMS, OR FROM LOW TO HIGH BEAMS	1. Ineffective SCCM microcontroller inputs or outputs.	1. Use a diagnostic scan tool and the appropriate diagnostic information for further SCCM microcontroller diagnosis.
	2. Ineffective BCM inputs or outputs.	2. Use a diagnostic scan tool to test the BCM inputs and outputs. Refer to the appropriate diagnostic information.