The exterior lighting system consists of the following lamps:

The headlamps may be turned on 2 different ways, if equipped with RPO T 82, automatic lamp control (ALC). First, when the driver places the headlamp switch in the ON position, for manual operation. Second, with ALC, and the headlamp switch placed in the OFF position.

The LH HDLP and RH HDLP fuse in the fuse block - underhood, supply battery positive voltage to both low and high beam lamps at all times. For manual operation or without RPO T 82, when the headlamp switch is in the ON position, the headlamp switch supplies ground directly to the headlamps and to the body control module (BCM) on the headlamp low or high beam signal circuit, depending on the position of the headlamp dimmer switch. The BCM uses this signal to determine if the conditions are present to illuminate the daytime running lamps or headlamps.

For ALC operation, the BCM receives a signal from the ambient light sensor indicating a low or high ambient (outside) light level. The ambient light sensor is a light sensitive transistor that varies its voltage signal to the BCM in response to changes to the outside (ambient) light level. Under the correct conditions the BCM grounds the headlamp relay control circuit energizing the headlamp control relay. The now closed relay supplies ground through the headlamp switch to the headlamps and the BCM on the headlamp low or high beam signal circuit, depending on the position of the headlamp dimmer switch. When the BCM grounds the headlamp relay control circuit, it also grounds the park lamp relay control circuit illuminating the park lamps. The headlamp relay is grounded at G203.

If the engine stalls with the headlamps in the ALC mode under low light conditions, the headlamps will be controlled OFF during cranking.

The conditions necessary for the BCM to activate the ACL mode are as follows:

The low beam headlamps operate at reduced intensity when in daytime running lamps (DRL) mode. The ground circuit to the switch input side of the DRL relay has a resistor in-line to reduce the intensity of the low beam headlamps for DRL operation. With RPO T 82, the body control module (BCM) receives a signal from the ambient light sensor indicating a low or high ambient (outside) light level. Without RPO T 82, when the headlamp switch is in the ON position, the headlamp switch supplies ground directly to the headlamps and to the BCM on the headlamp low or high beam signal circuit, depending on the position of the headlamp dimmer switch. The BCM uses these signals to determine if the conditions are present to illuminate the daytime running lamps.

Under the correct conditions the BCM grounds the DRL relay control circuit energizing the DRL control relay. The now closed relay supplies ground directly to the low beam headlamps and to the BCM on the headlamp low beam signal circuit. The low beam headlamps now illuminate with reduced intensity. The DRL relay is grounded at G101. Any time the headlamps or park lamps are illuminated the DRL will not illuminate.

The conditions necessary for the BCM to illuminate the DRL are as follows:

The FOG LP fuse in the fuse block - underhood supplies battery positive voltage to the switch side of the fog lamp relay at all times. When the fog lamp switch is pressed, it supplies voltage on the front fog lamp switch signal circuit to the body control module (BCM). The BCM then supplies ground to the coil side of the fog lamp relay, energizing the relay. The switch side of the fog lamp relay then supplies voltage to both front fog lamps. The front fog lamps are connected to ground at G101. The park lamps or headlamps must be ON for the fog lamps to operate.

The park lamps consist of the park, tail, marker, and license lamps. These lamps are illuminated any time the headlamp switch is in the park, headlamp on position, or anytime the body control module (BCM) illuminates the headlamps. The PARK fuse in the fuse block - instrument panel (I/P) supplies voltage to both the coil and switch input side of the park lamp relay. The BCM controls the park lamp relay by grounding the park lamp control circuit energizing the relay.

For automatic lamp control (ALC) the BCM receives a signal from the ambient light sensor indicating a low or high ambient (outside) light level. Under low light conditions, the BCM grounds the park lamp relay control circuit energizing the park lamp relay. The now closed relay supplies voltage on the park lamp supply voltage circuit directly to the lamps. The BCM always turns ON the park lamps and headlamps together when in the ALC mode.

For manual operation, when the headlamp switch is in the park position, the headlamp switch supplies ground to the BCM on the park lamp switch signal circuit. In response, the BCM grounds only the park lamp relay control circuit, and the lamps illuminate as stated above.

The conditions necessary for the BCM to activate the ALC mode are as follows:

The TURN fuse in the fuse block - instrument panel (I/P) provides ignition positive voltage to the flasher module. The turn signal lamps may only be activated with the ignition switch in the ON position. When the turn signal switch is placed in either the left or right position, current flow is from the flasher module output to the turn signal switch assembly. The flasher module then sends an ON-OFF voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator.

The HAZARD fuse in the fuse block - instrument panel (I/P) provides battery positive voltage to the flasher module. When the hazard switch is activated, the flasher provides an ON-OFF voltage to all of the turn signal lamps and both turn signal indicators. The lamps receive a ground at G101, G401, or G403.

The 15A BRAKE fuse located in the fuse block - underhood, 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 both left and right stop lamp assemblies, the center high mounted stop lamp (CHMSL), and the engine control module (ECM). The stop lamps are grounded at G401 and G403. The CHMSL is grounded at G301.

The 10A BACKUP fuse in the fuse block - underhood supplies ignition positive voltage to the park/neutral position (PNP) switch of the automatic transmission or backup switches for manual transmission. When the transmission is placed in reverse, the switch supplies voltage to the back up lamps and the inside rearview mirror. The back up lamps receive ground at G401 and G403.