Exterior Lighting System

HEADLAMP POWER
The headlamp switch is a direct input to the BCM. The BCM sends a BUS message to the IPM informing it of a headlamp switch status change. The IPM then turns on power to the headlamps through four "fuseless" circuits. These circuits are electronically controlled and continuously monitored for malfunctions. Power is supplied to each filament in a separate circuit. On vehicles with HID lamps for low beam, the IPM provides power to the HID module which in turn, turns the lamps on. For vehicles equipped with daytime running Lamps (DRL), the IPM electronically steps down the headlamp voltage to provide the desired illumination. The DRLs will automatically extinguish when the hazards are activated and will come back on when the hazards are deactivated.

HEADLAMP SWITCH
The Headlamp Switch uses a multiplexed (MUX) circuit to the Body Control Module (BCM). The Headlamp Switch controls the Fog lamp relay, Park lamps and the Low and High Beam headlamps. The BCM then sends a signal through the PCI Bus line to the IPM as to what state the switch has selected. The IPM energizes the high side output drivers to turn ON the desired lamps.

FRONT PARK AND SIDE MARKER LAMPS
The park lamp switch is a direct input to the BCM. The BCM sends a BUS message to the IPM informing it to turn on the park and side marker lamps. The park lamp relay is then powered through low side control of the IPM. This circuit is electronically controlled and continuously monitored for malfunctions. The IPM provides power through a high side driver.

FRONT FOG LAMP
The fog lamp switch is a direct input to the BCM. The BCM sends a BUS message to the IPM informing it to turn on the fog lamps. This circuit is electronically controlled and continuously monitored for malfunctions. Fog lamp functionality is not equipped on all vehicles. The IPM "learns" that the vehicle is equipped with fog lamps by reading the BCM BUS message. The Fog lamps can only be ON when the park and low beams are ON. If the high beams are switched ON then the Fog lamps will be automatically turned OFF.

EXTERIOR LIGHTING BATTERY SAVER
The BCM monitors status for the control of the Park Lamps, Headlamps and Fog Lamps. If any exterior lamps are left ON after the ignition is turned OFF, the BCM will send this information to the IPM, which will then turn the drivers OFF after 3 minutes.

AUTO HEADLAMPS
This feature is available on vehicles equipped with both the Electrocromatic Mirror (ECM) and the Compass/Mini-Trip Computer (CMTC). When the BCM detects a day/night signal from the CMTC, an ECM is present and Auto Headlamp mode is selected.