The headlamps are controlled by the multifunction lever on the left side of the steering column. They will come on with the ignition switch in ON position. If the headlamp switch is ON and the ignition key is in ACC or LOCK position, the headlamp will be turned off automatically. Turning the headlamp switch to the first position turns on the parking lamps, the license plate lamps, and the instrument panel illumination. Turning the switch to the second position turns on all of the previous lamps and the headlamps. Turning the switch OFF turns off all the lamps.

The headlamps may be turned on in 2 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC the headlamps will be in DRL operation in daylight conditions, or headlamp operation in low light conditions.

Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the headlamp switch on input circuit when the headlamp switch is in the HEAD position. When the headlamp switch is in the AUTO position, the BCM determines headlamps ON/OFF by the voltage from the ambient light sensor.

The headlamps high beam and low beams are also controlled by this lever. When the headlamps are on, pushing the lever away from the driver until the switch clicks changes the lamp from low beam to high beam. An indicator lamp on the instrument cluster assembly will come on when the high-beam headlamps are on. To return the headlamps to low beams, pull the lever toward the driver. The headlamps must be aimed for proper illumination of the road. Headlamp aim should be checked whenever a new headlamp assembly is installed or when service or repairs to the front end may have disturbed the headlamp assembly or its mountings.

The ambient light sensor is a light-sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes in the outside (ambient) light level. When the BCM receives this signal the BCM either turns ON the just the low beam headlamps at reduced intensity for the daytime running lamp (DRL) operation or turns ON the low beam headlamps and the exterior lamps for automatic lamp control (ALC). Any function or condition that turns ON the headlamps will cancel the DRL operation. Thirty seconds after you start the engine with the headlamp switch in the OFF position, the DRL will perform one of two actions:

The DRL operates when the ignition switch is in the RUN position, the parking brake is not set and the transmission is not in the PARK position When these conditions are met and the DRL ambient light sensor indicates daylight conditions the DRL will illuminate.

The parking lamps can be turned on by turning the headlamp switch to the first position. The parking lamps can be turned off by turning the switch off.

When the turn signals are activated, the appropriate turn signal lamps flash to signal a turn. The front, the rear, and the side turn signals work only when the ignition is on.

The front and the rear turn signals are controlled by the multifunction lever on the left side of the steering column. Moving the lever all the way up or down past the detent will turn on the turn signals. When the turn is complete, the lever will automatically release, and the front and the rear turn signals will stop flashing.

For changing lanes or shallow turns in which the steering wheel does not turn far enough to cancel the signal, move the signal to the first detent and hold it there. The turn signal will cancel when the lever is released.

The fog lamp switch is on the instrument panel above the audio system. To use the fog lamps, first turn on the headlamps. Then, push the fog lamp switch. The indicator light in the instrument cluster will illuminate to indicate that the fog lamps are on. Push the switch again to turn off the fog lamps. The indicator light will then go off.

The fog lamps must be aimed for proper illumination of the road. Fog lamp aim should be checked when a new bulb is installed or if service or repairs to the front end may have disturbed the fog lamp assembly or its mountings.

The taillamps, stoplamps, backup lamps, and turn signals are one assembly.

Turning on either the headlamps or the parking lamps will also turn on the taillamps. When the brake pedal is pushed, the taillamps will glow more brightly to serve as stoplamps.

The center high-mounted stoplamp is in the rear window and will come on when the brake pedal is pressed.

The backup lamps will come on when the transaxle is shifted into reverse. On a vehicle with an automatic transaxle, the backup lamps are activated by the park/ neutral position switch.

The license plate lamps will come on when the headlamps or the parking lamps are on. The license plate lamps are mounted on the rear deck lid, above the license plate.

The XBCM shall be the master of communications with the vehicle Alarm Siren Module. The XBCM shall arm, disarm, and set alarm based on the current CTD or VTD theft state. The XBCM will receive commands from GMLAN signals that define the current CTD state of the vehicle.

The XBCM shall provide for control of the auxiliary CTD horn relay.

Legal regulations require the turn signal feature to be capable of detecting when one or more of its lamps are not functioning. For this reason, the XBCM shall track the state of the Left and the Right side Trailer Stop/Turn lamps separately to determine if a Stop/Turn signal is malfunctioning.