Exterior Lighting Systems

EXTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION

EXTERIOR LAMPS
The exterior lighting system consist of the following lamps:
- The headlamps
- The daytime running lamps (DRL)
- The park, tail and marker lamps
- The turn signal/hazard lamps
- The stop lamps
- The backup lamps

HEADLAMPS
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.

If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.

The high beam indicator is illuminated when the instrument cluster receives a class 2 serial data message from the BCM that the high beams are illuminated.

HIGH BEAMS
The high beam headlamps receive voltage from the HDLP-HIBM relay located in the underhood fuse block. The BCM controls the relay on the headlamp high beam relay control circuit. High beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is grounded, the BCM grounds the headlamp high beam relay control circuit, illuminating the high beam headlamps. The right and left high beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G101.

LOW BEAMS
The low beam headlamps receive voltage from the HDLP-LOBM relay located in the underhood fuse block. The BCM controls the relay on the headlamp low beam relay control circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is open, the BCM grounds the headlamp low beam relay control circuit, illuminating the low beam headlamps. The right and left low beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G101.

DAYTIME RUNNING LAMPS (DRL)
The DRL are a function of the front turn signal lamps. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position, and the headlamp switch is in the OFF position. When the BCM receives these signals it will signal the turn/hazard flasher module to turn on the DRL by grounding the DRL low control signal. The turn/hazard flasher module supplies voltage to the DRL on the right and left DRL/turn supply voltage circuits. If a front turn signal lamp is inoperative the DRL will not operate.

The DRL can be deactivated by turning the headlamp switch to the DRL OFF position while the DRL are operating. The DRL defeat position of the headlamp switch is a momentary ground signal to the BCM to command the DRL function ON or OFF. After each key cycle the BCM will default to the DRL ON function.

PARK, TAIL AND MARKER LAMPS
The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in the PARK or HEAD position. The headlamp and panel dimmer switch supplies a ground signal to the BCM on the park lamps switch on signal circuit. 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 turned on the BCM energizes the park lamp relay. Current flow is from the park lamp relay to these fuses in the body fuse block:
- FR PARK
- LR PARK
- RR PARK
- TRLR PARK
- UPFTR PRK

The front park and marker lamps are grounded at G100 and G101. The rear park and license lamps are grounded at G401 and 402.

TURN SIGNAL/HAZARD LAMPS
The IGN E 10 A fuse in the underhood fuse block supplies battery positive voltage to the turn signal switch assembly. Ground for the hazard switch is from G302. The FLASHER 15 A fuse in the underhood fuse block supplies battery positive voltage to the turn/hazard flasher module. When the turn signal switch is placed in either the left or right position, a voltage signal is completed from the turn signal switch to the turn/hazard flasher module. When the hazard flasher switch is activated, a ground signal is completed from the hazard switch to the turn/hazard flasher module. The turn/hazard flasher module then sends an on-off voltage signal to the appropriate turn signal lamps, or to all turn signal lamps for hazard operation through these fuses:
- DR TRN MIR, in the body fuse block
- PASS TRN MIR, in the body fuse block
- LR STOP/TRN, in the body fuse block, and in the underhood fuse block for RPO UY7
- RR STOP/TRN, in the body fuse block, and in the underhood fuse block for RPO UY7
- LR TURN in the underhood fuse block
- RR TURN in the underhood fuse block
- LT DRL/TRN in the underhood fuse block
- RT DRL/TRN in the underhood fuse block

The audio chime is also activated when the turn signals are on. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G100 and G101. The rear turn signals are grounded at G401 and 402. The mirror turn signals are grounded through a splice pack at G347.

STOP LAMPS
The STOP LP 15 A 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 STOP/CHMSL fuse and through the turn/hazard flasher module to the LR STOP/TRN and RR STOP/TRN fuses in the body fuse block or the LR TURN and RR TURN fuses in the underhood fuse block. The voltage from the STOP/CHMSL fuse is to the CHMSL and cruise control. The voltage from the LR STOP/TRN and RR STOP/TRN fuses is to the rear stop lamps. The voltage from the LR TURN and RR TURN fuses is to the trailer stop/turn relays. The rear stop lamps are grounded at G401 and 402. The CHMSL is grounded at G401

BACKUP LAMPS
The B/U LP 20 A fuse in the underhood fuse block supplies battery positive voltage to the normally open park neutral position (PNP) switch. When driver places the gear selector lever is in the REVERSE position, the switch closes and the voltage is from the switch to the powertrain control module (PCM). The PCM signals the BCM on the class II serial data circuits that the backup lamps are requested. The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic day/night mirror. The backup lamps are grounded at G401. Voltage for the backup lamp supply voltage, without RPO YF7 the courtesy lamp supply voltage, and with RPO YF7 the courtesy lamp high control circuits is from the TBC 2 fuse 18 in the underhood fuse block directly through the BCM to these circuits.