The exterior lighting system consists of the following lamps:

The door lock switch backlighting of the interior door lock switches are also supplied voltage by the courtesy lamp supply voltage circuit and will only operate while the park lamps are illuminated. This circuit is diagnosed as part of the exterior lamp lighting system.

Major components of this system are the body control module (BCM), headlamp relay, beam select relay, ambient light sensor, headlamp and panel dimmer switch, turn signal/multifunction switch, park brake switch, and the low and high beam headlamps.

The headlamps may be turned ON in 2 different ways. First, when the driver places the headlamp switch in the ON position, normal operation occurs. Second, when the headlamp switch is placed in the AUTO position, automatic lamp control (ALC) operation occurs. During ALC control, the headlamps will be OFF in daylight conditions or in low/high beam operation in low light conditions.

The headlamp relay receives battery positive voltage directly from the battery. The BCM supplies a ground signal to the headlamp relay for normal headlight operation. The BCM also supplies voltage to the beam select relay coil for high beam headlight operation. When the driver places the headlamp switch in the ON position and the dimmer switch is in the low beam position, the headlamp relay supplies current flow through the left and right low beam headlamp fuses to both low and high beam headlamps. Both low beam headlights are grounded through the beam select relay. When activated, the dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-pass (FTP) position from G106. The BCM then energizes the beam select relay which switches the headlamp grounds from the low beam headlight bulbs to the high beam headlight bulbs illuminating the high beam headlights. With the headlights in the low beam position, the high beams may be momentarily turned ON or flashed by activating the FTP portion of the switch.

The instrument panel cluster (IPC) illuminates the high beam indicator when the BCM detects that the high beams are requested. The IPC receives a class 2 message from the BCM requesting illumination.

The Headlamps On at Exit and Perimeter Lighting modes can be adjusted using the steering wheel controls to select the desired function as displayed in the driver information center (DIC). The Headlamps On at Exit selection will allow the driver to customize the period of time that the headlamps remain illuminated upon exiting the vehicle. This period can be adjusted from 0-180 seconds. The Perimeter Lighting feature allows the driver to select if they desire the headlamps and backup lamps to illuminate when the door UNLOCK button on the key fob is activated. This feature can be turned ON or OFF by using the DIC steering wheel control buttons.

The ambient light sensor is a light sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes to the outside (ambient) light level. When the BCM receives this signal, it will either turn ON the daytime running lamps (DRL) or the headlamps for auto headlamp operation. Any function or condition that turns ON the headlights will cancel the DRL operation. With the headlight switch in the AUTO position, the headlights will either be turned ON or OFF, after an approximate 8 second delay depending on whether daylight or low light conditions are sensed. On early production vehicles built prior to VIN 5GTDN136068233825, when the ambient light sensor signals the BCM for DRL operation in daylight conditions, the BCM illuminates the front turn signal lamp bulbs at a constant rate. For later production vehicles built after that VIN, when the ambient light sensor signals the BCM for DRL operation in daylight conditions, the BCM illuminates the low beam headlamps at a reduced intensity utilizing the DRL relay. The DRL will operate when the ignition switch is in the RUN position, the headlamp and panel dimmer switch is in the AUTO position, the gear selector is not in the PARK position, and the parking brake is released. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.

DRL operation can be temporarily disabled by momentarily placing the headlamp switch in the OFF position. This will cancel DRL operation until the switch is momentarily placed in the OFF position again or until the next ignition key cycle occurs. Canadian requirements prohibit disabling DRL operation therefore the Canadian export vehicles are not equipped with the DRL defeat feature.

With both the ignition switch in the RUN position and the park lamps or low beam head lamps ON, the fog lights will illuminate when the driver presses the fog lamp switch. The FOG LP fuse in the underhood fuse block supplies battery positive voltage to the fog lamps. With the headlamp switch is in either the park or headlamp position and the fog lamp switch is pressed, the body control module (BCM) will energize the fog lamp relay control circuit. The current flow is from the fog lamp relay to both front fog lamps and to ground G105. The state of the fog lamps, either ON or OFF, will remain the same until the fog lamp switch is pressed again, or the ignition switch is cycled OFF and ON. Fog lamp operation will be cancelled whenever the park lamps are turned OFF or the high beam headlights have been selected.

The park, tail, marker, license and clearance lamps are turned ON when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested. The underhood fuse block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are requested ON, the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the individual park lamp circuit fuses and to their respective park, tail, marker, license and clearance lamps. The front park, marker, tail, license and clearance lamps are grounded at G105, G350, G340 and G420. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, the park, tail, marker, license and clearance lamps will remain ON until turned OFF or the battery runs dead.

The FRT/TRN/HAZ/CRTSY/MIRR and REAR/TRN/HAZ fuses in the underhood fuse block supplies battery positive voltage to the body control module (BCM). When the turn signal switch is placed in either the left or right position, a signal is sent to the BCM to illuminate the desired turn signal lamps. The BCM has an internal flasher that sends an ON-OFF voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator. When the hazard switch is pressed, a separate ground signal is sent to the BCM to activate and flash all turn signal lamps including both IPC turn indicators. The front and rear turn signals are grounded at G105, G350 and G340. The sound for the turn signal indicators is produced by the IPC.

The STOP fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to the body control module (BCM), electronic brake contol module (EBCM), powertrain control module (PCM), and the center high mounted stop lamp (CHMSL) which is grounded at G350. The EBCM may also supply battery positive voltage to activate the stop lamps during specific ABS events.

The BCK/UP LPS fuse in the underhood fuse block supplies battery positive voltage to the normally open park/neutral position (PNP) switch of a vehicle equipped with an automatic transmission or the backup lamp switch if equipped with a manual transmission. When the driver places the gear selector lever is in the REVERSE position, the switch closes and the current flow is from the switch to the backup lamps. The backup lamps are grounded at G350 and G340.

The off-road lamps are available in several configurations with lights mounted on the roof and on the front brush guard. The lamps are controlled by a single, rocker type switch, located on the instrument panel. When the switch is closed, voltage is supplied to the relays on the off-road lamps relay control circuit. When the relays are energized, voltage is supplied to the off-road lamps.