Lamps/Lighting - Exterior (Service Information): Operation: Headlamps

The headlight system includes the IPC, the Steering Column Control Module (SCCM), the Body Control Module (BCM), the headlight switch and the multi-function switch on the steering column. The headlight bulbs have a path to ground at all times. The FEM harness has takeouts with eyelet terminals that are secured to the front end sheet metal within the engine compartment. The BCM will store a Diagnostic Trouble Code (DTC) for any shorts or opens in the headlight circuits.

The BCM monitors a hardwired input to determine the status of the headlight switch. The BCM also monitors electronic headlight beam select switch status messages received from the SCCM over the CAN data bus. The BCM responds to these inputs by providing voltage output to the headlight bulbs through high side drivers on the right and left headlight feed circuits to illuminate the headlights, and controls the high and low beam shutter operation through high side drivers on the right and left high beam feed circuits. The BCM also sends the appropriate electronic headlight beam status messages to the IPC to control the illumination of the high beam indicator.

The BCM also remembers which beams (LOW or HIGH) were selected when the headlights were last turned OFF, and energizes those beams again the next time the headlights are turned ON. The BCM provides a battery saver (load shedding) feature for the headlights, which will turn these lamps OFF if they are left ON for more than about eight minutes when the ignition switch status is LOCK. The SCCM and the BCM each provide a fail-safe feature for the headlights, which will cause the BCM to turn the low beam headlights ON automatically if there is no input available from the headlight switch or the multi-function switch. The BCM also provides a fail-safe feature for the headlights that will turn the headlights ON automatically whenever a loss of CAN bus communication is detected when the ignition switch status is ON.

Each headlight includes an integral reflector adjustment screw to be used for static aiming of the headlights.

Headlights ON with Wipers (HOWW) 

HOWW is a configurable feature designed to automatically turn on the headlights when the wiper system is activated. When the engine is running, the wipers are activated and the headlight switch position is in Auto, the HOWW system will activate. With the headlight switch position in Auto the BCM monitors three signals to determine when to actuate the headlight system:

1. HOWW request signal
2. Auto Headlight state
3. Park Lamp state

To cancel the HOWW feature, turn the headlight switch to any position other than Auto.

Headlights On With Snow (HOWS) 

HOWS is designed to automatically turn on the headlights when the Terrain Select switch is switched to Snow Mode for increased safety while driving in snowy conditions. HOWS is not a customer programmable feature. When the ignition state is RUN, the engine is running, the Terrain Select switch is set to Snow Mode and the headlight switch position is set to Auto, the BCM will wait one second before actuating the headlight system. If the auto headlights feature becomes active while HOWS is active, the auto headlights feature will have the higher priority. To exit the HOWS feature while leaving the Terrain Select switch in Snow Mode, the headlight switch will need to be switched to any position other than Auto.