The exterior lighting system includes the following components:

The headlamps may be turned on 2 different ways. First, when the driver places the headlamp switch is placed in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the OFF position, for Daytime Running Lamps (DRL) operation in night mode.

The PARK LP fuse and the HEADLAMPS circuit breaker, supply battery positive voltage to the headlamp switch and headlamp dimmer switch. When the headlamp switch is placed in the HEAD position, it provides voltage to the headlamp dimmer switch. The headlamp circuit continues through the headlamp dimmer switch and, depending on the position of the headlamp dimmer switch, is connected to either the low beam or high beam headlamps. The headlamps are grounded at G101 for the LH headlamp and G102 for the RH headlamp.

With the headlamp dimmer switch in the low beam position, the high beams may be momentarily turned on or flashed with the headlamp dimmer switch handle. When the headlamp dimmer switch handle is pulled toward the driver, the flash-to-pass switch closes providing voltage to the high beam circuit. Both high beams will remain on until the driver releases the switch handle. If the low beam headlamps were on during a flash-to-pass operation, they will remain on. The headlights may be switched to high beam by pulling the headlamp dimmer switch handle toward the driver until the headlamp dimmer switch is activated. When the headlamp dimmer switch is placed in the HIGH BEAM position, the high beam circuit provides voltage to the high beam indicator in the IP.

If the headlight switch is left in the ON position, the headlights will remain on until turned off or the battery runs dead.

The daytime running lamps (DRL) are the front turn signals. The front turn signals are designed to automatically illuminate in daytime light conditions.

The ambient light sensor is a light sensitive transistor that varies its voltage signal to the daytime running lamps (DRL) control module in response to changes to the outside (ambient) light level. When the DRL module receives this signal it will either turn on the daytime running lamps (DRL) or the automatic headlamps depending on the ambient light level. When the daytime running lamps (DRL) control module detects daylight conditions, it will turn on the front turn signals.

In the daylight conditions, the ambient light sensor detects daylight and the DRL control module applies voltage to the LH and RH front turn signal lamps illuminating the lamps under the following conditions:

The DRL control module will not operate the daytime running lamps, if the park brake is applied before the ignition switch is turned to the RUN position. This allows the driver to start the vehicle and keep the daytime running lamps OFF, as long as the park brake is applied. The DRL control module will activate the daytime running lamps when the park brake is released with the ignition switch in the RUN position. This feature functions only when the park brake is applied before the ignition switch is turned to the RUN position.

When the turn signal switch place in either the LH or RH position, pulsating voltage is supplied to the DRL control module. The DRL control module senses the voltage and disengages the DRL function of the appropriate front turn signal. The DRL control module then relays the turn signal voltage to the front turn signal and the front turn signal will flash .

The Daytime Running Lamps (DRL) control module will not operate the headlamps or exterior lamps if the park brake is applied before the ignition switch is turned to the RUN position. This allows the operator to start the vehicle and keep the headlamps off, as long as the park brake is applied. The DRL module will activate the headlamps when the park brake is released with the ignition switch in the RUN position. This feature will only function when the park brake is applied before the ignition switch is turned to the RUN position. The headlamps will not turn off if the park brake is applied after the ignition switch is turned to the RUN position.

The automatic headlamps and parklamps are designed to automatically illuminate when the ignition is RUN and the outside (ambient) light level is low, as in nighttime conditions. Light levels are detected by the ambient light sensor, a light sensitive transistor that varies its voltage signal to the daytime running lamp (DRL) control module in response to changes to the ambient light level. When the DRL control module receives a low light signal from the ambient light sensor, it will then turn on the headlamps and parklamps. The daytime running lamps will not operate when the automatic headlamps and parklamps are on.

When the ambient light sensor detects low light levels, the DRL control module turns OFF the daytime running lamps and turns on the headlamps and parklamps under the following conditions:

If the engine stalls with the DRL control module in the low light mode, the DRL control module turns OFF the headlamps while the engine is being cranked. The parklamps will remain ON while the engine is being cranked.

The Daytime Running Lamps (DRL) system is designed to automatically operate the low beam headlamps and the tail lamps, whenever the ignition switch is in the RUN position with the engine running.

The PARK LP fuse and the HEADLAMPS circuit breaker supply battery positive voltage to the DRL control module. The DRL/HVAC/TEMP fuse provides ignition positive voltage to the DRL control module. When the engine is running, the engine oil pressure (EOP) switch sends a signal to the DRL control module. The DRL control module then supplies battery voltage to the low beam headlamps and tail lamps. The DRL control module is grounded at G200.

The PARK LP fuse and the FOG LP fuse supply battery voltage to the headlamp switch and the fog lamp relay contacts. When the headlamp switch is in HEAD or PARK and the driver presses the fog lamp switch, voltage is applied to the fog lamp relay coil. The fog lamp relay coil is grounded through the high beam headlamp filaments. The relay energizes and applies voltage to the fog lamps through the fog lamps supply voltage circuit. Because the coil of the FOG LAMP relay is grounded through the high beam filaments, the relay will de-energize any time the high beams are ON. The fog lamps can also be activated with the headlamp switch OFF, during automatic headlamp operation. When the automatic headlamps are on, the DRL control module applies voltage to the fog lamp switch and to the exterior lights.

The rear fog lamp module requires the headlamps to be ON in order to turn ON the rear fog lamps. The HEADLAMP circuit breaker an RR FOG LP fuse provide battery voltage to the headlamp switch and rear fog lamp relay. When the headlamps are on, battery voltage is applied to the rear fog lamp module. The rear fog lamp switch is a momentary contact switch that, when pressed, provides a ground signal to the rear fog lamp module. When the rear fog lamp module receives the fog lamp switch ON input from the fog lamp switch and the headlamps are ON, the rear fog lamp module energizes the rear fog lamp relay. When energized the rear fog lamp relay provides battery voltage to the rear fog lamps. If the rear fog lamp switch is pressed again, the rear fog lamp module will de-energize the rear fog lamp relay. If the headlamps are turned OFF while the rear fog lamps are on, the rear fog lamps will turn off. If the headlamps are turned back ON, the rear fog lamps will not turn on unless the rear fog lamp switch is pressed again.

The park lamp, sidemarker lamps, tail lamps, and license lamps, are turned on when the headlamp switch is placed in either the PARK or HEAD position, or anytime the headlights are requested. With the headlamp switch placed in the OFF position, and the Daytime Running Lamps (DRL) ambient light sensor indicating low light conditions, the Daytime Running Lamps (DRL) control module will operate the park lamp, sidemarker lamps, tail lamps, and license lamps. The PARK fuse supplies battery voltage to the headlamp switch and DRL control module. Current flow is from the headlamp switch or the DRL control module to the park lamp, sidemarker lamps, tail lamps, and license lamps. The LF park lamp is grounded at G101 and the RF park lamp is grounded at G102. The side marker lamps are grounded through the corresponding rear turn signal lamps when the rear turn signal lamps are inactive. The remaining lamps are grounded a G401.

The tail lamps, headlamp position lamps, and license lamps, are turned on when the headlamp switch is placed in either the PARK or HEAD position, or anytime the headlights are requested. With the headlamp switch placed in the OFF position, and the engine running, the Daytime Running Lamps (DRL) control module will operate the tail lamps. The PARK fuse supplies battery voltage to the headlamp switch and DRL module. Current flow is from the headlamp switch to the headlamp position lamps and license lamps. The tail lamps receive the headlamp switch voltage via an inactive DRL control module. For DRL operation current flow is from the DRL control module to the tail lamps only. The LF headlamp position lamp is grounded at G101 and the RF headlamp position lamp is grounded at G102. The remaining lamps are grounded a G401.

The turn signal lamps may only be activated with the ignition switch in RUN or BULB TEST position. The T/SIG fuse supplies ignition voltage to the turn signal switch. When the turn signal switch is placed in either the left or right position, the turn signal switch sends an ignition voltage to the hazard lamp/turn signal flasher, which sends an on-off signal to the turn signal switch. When the turn signal switch receives the on-off signal it will send that signal to the following lamps on the LH or RH side:

The turn signal switch also sends a separate on-off signal to the Daytime Running Lamps (DRL) control module, which relays the signal to the appropriate front turn signal. The front turn signals are grounded at G101 and G102. The rear turn signals are grounded at G401. The sidemarker lamps are grounded through the corresponding front parklamp.

The sideview mirror turn signals are a bank of LEDs placed behind the mirror glass.

The hazard lamps operate on battery voltage. The HAZARD fuse supplies battery voltage to the turn signal switch. When the hazard switch is pressed, the turn signal switch sends battery voltage to the hazard lamp/turn signal flasher, which sends an on-off signal to the turn signal switch. The turn signal switch send the on-off signal to all the turn signal lamps, causing all the lamps to flash including both IPC turn signal indicators. The hazard lamp/turn signal flasher is grounded at G200.

When the parklamps are ON, the sidemarker lamps receive voltage from the park lamp supply voltage circuit and illuminate. The sidemarker lamp is grounded through the corresponding rear turn signal. When the turn signal switch is place in the left or right hand position, the rear turn signal illuminates and the sidemarker lamp will loose its ground, causing the sidemarker lamp to turn off when the turn signals are on and to illuminate again when the turn signal is off.

The HAZARD fuse and T/SIG fuse, supplies battery and ignition positive voltage to the turn signal switch. The turn signal lamps may only be activated with the ignition switch in RUN or BULB TEST position. When the turn signal switch is placed in either the left or right position, current flow is from the turn signal switch to the hazard lamp/turn signal flasher and back to the turn signal switch assembly. The hazard lamp/turn signal flasher sends an on-off voltage signal to the turn signal switch, which sends the on-off signal to either the left or right rear turn signal, front turn signal, repeater lamp, and their Instrument Cluster Panel (IPC) indicator. The hazards lamps operate on battery voltage. When the hazard switch is pressed, all the turn signal lamps will flash including both IPC turn signal indicators. The hazard lamp/turn signal flasher is grounded at G200. The LF turn signal and LF repeater lamp are grounded at G101. The RF turn signal and RF repeater lamp are grounded at G102. The rear turn signals are grounded at G401.

The stoplamp fuse in the fuse block, supplies battery positive voltage to the normally open stoplamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both left and right stoplamp assemblies and to the Center High Mounted Stoplamp (CHMSL). The stop lamp and Center High Mounted Stoplamp (CHMSL) is are grounded at G401.

The B/U LAMP fuse in the junction block - underhood, supplies battery positive voltage to the transmission range switch. When the driver places the gear selector lever in the REVERSE position, the switch closes and the current flow is through the backup lamp switch to both backup lamps. The backup lamps are grounded at G401.

The T/SIG fuse supplies ignition voltage to the backup relay switch contacts. The B/U LAMP fuse in the junction block - underhood, supplies battery positive voltage to the transmission range switch. When the driver places the gear selector lever in the REVERSE position, the transmission range switch closes and the current flow is through to the backup relay coil, energizing the relay. When the backup relay is energized the right and left backup lamps receive voltage through the back up lamp supply voltage circuit . The backup lamps are permanently grounded through to G401.

Fog Lamp

The IPC illuminates the fog lamp indicator when the fog lamp switch sends a high output to the IPC.

High Beam

The IPC illuminates the high beam indicator when the headlamps are on and the headlamp dimmer switch is in the high beam position.

Trailer Towing

The IPC illuminates the trailer towing indicator when the trailer tow is connected and the left or the right turn signal is activated. The hazard lamp/turn signal flasher sends a high output to the instrument cluster.

Turn Signals

The IPC illuminates the right or left turn signal indicator when the IPC detects a turn signal request or a hazard request.

Driver controls include the following components.

These three modules process the inputs and the controls: