Lamps/Lighting - Exterior

EXTERIOR LAMPS / LIGHTING

Lamp System
Lighting circuits are protected by fuses. Lighting circuits require an overload protected power source, ON/OFF device, lamps and body ground to operate properly. Plastic lamps require a wire in the harness to supply body ground to the lamp socket. Replace sockets and bulbs that are corroded.

Some of the interior and exterior lighting functions are governed by the Body Control Module (BCM). The headlamp, dome, and the door ajar switches provide signals to the BCM. The BCM in turn sends a Programmable Communication Interface (PCI) bus message to the Front Control Module (FCM) to enable the necessary drivers to set the required illumination configuration.

Wire connectors can make intermittent contact or become corroded. Before coupling wire connectors, inspect the terminals inside the connector. Male terminals should not be bent or disengaged from the insulator. Female terminals should not be sprung open or disengaged from the insulator. Bent and sprung terminals can be repaired using needle nose pliers and pick tool. Corroded terminals appear chalky or green. Corroded terminals should be replaced to avoid recurrence of the problem symptoms.

Begin electrical system failure diagnosis by testing related fuses in the fuse block and intelligent power module. Verify that bulbs are in good condition and test continuity of the circuit ground. Refer to the appropriate wiring information.

Automatic Headlamp System
This feature is available on vehicles equipped with both the Electrochromatic Mirror (ECM) and the Compass/Mini-Trip Computer (CMTC).

The Automatic Headlamp system turns the instrumentation and exterior illumination lamps ON when the ambient light levels are Night and the engine speed is 450 rpm or above, and OFF when light levels are Day.

Automatic headlamps are controlled by the Body Control Module (BCM). With the headlamp switch in the AUTO position, the BCM will control the headlamp, parking, side marker, tail and instrumentation lamps based on ambient light levels. Ambient light levels are monitored by the BCM using the Day/Night signal and Electrochromatic Mirror (ECM) present from the Compass Mini Trip (CMTC) located on the front windshield in front of the rear view mirror ECM. Ambient light readings are averaged to limit cycling the lamps ON and OFF when passing through areas with varying light levels. The automatic headlamps will only function when the engine is running with RPM> 450. When the headlamp switch is in the AUTO position (Automatic mode), the Headlamp Time Delay system will function when the ignition switch is placed in any position other than run/start.

Daytime Running Lamps
Operating the high-beam headlamps at reduced power provides daytime running lamps, which are required on all new Canadian vehicles.

Power is reduced using pulse-width modulation to the high beams, where by the power is switched ON and OFF rapidly instead of remaining ON continuously. The duration and interval of the power pulses is programmed into the FCM.

Headlamps On With Windshield Wipers
For vehicles equipped with the Automatic Headlamp System, the instrumentation and exterior illumination lamps will be turned ON when the headlamp switch is in the AUTO position, RPM > 450 and the windshield wipers have been in the intermittent, low or high mode of operation for more than ten seconds. When the windshield wipers are turned OFF the Body Control Module will determine if the instrumentation and exterior illumination lamps should remain ON base upon the current ambient light level.

Headlamp System
The configuration of the headlamp system of headlamps, park lamps and fog lamps is determined by the BCM. The BCM determines the lighting configuration as a result of the inputs from the ignition switch, headlamp switch and multi-function switch. A PCI bus is transmitted from the BCM to the FCM to enable the necessary drivers to set the illumination configuration. Four wires are connected between the headlamp switch and the BCM. The first wire contains information regarding the position of the headlamp switch (Off, Automatic Headlamps, Automatic Headlamp switch fog, Park with Fog, Head, or Head with Fog Lamps). The second wire contains information regarding the position of the dimmer switch (Dome Lamp, Daytime Brightness, Dimming Level or OFF). The third wire is a dedicated signal return (ground) wire. The fourth wire provides power to the front fog lamp indicator.

The headlamp system will default to headlamps ON position when ignition switch is ON and when an open or short circuit failure occurs ON the headlamp switch input. The system will return to normal operation when the open or short is repaired. A fault will be reported by the BCM when a failure occurs ON the dimmer or headlamp switch input.

If the exterior lamps are ON and the headlamp switch is in any position other than OFF or AUTO and with the ignition switch OFF (LOCK) after 3 minutes the BCM sends a message via PCI bus to the FCM informing the FCM to turn OFF the headlamps, park lamps and fog lamps. This feature prevents the vehicle battery from being discharged when the vehicle lights have been left ON.

Headlamp Power
The headlamp switch is a direct input to the BCM. The BCM sends a BUS message to the FCM informing it of a headlamp switch status change. The FCM then turns on power to the headlamps through four "fuseless" circuits. These circuits are electronically controlled and continuously monitored for malfunctions. Power is supplied to each filament in a separate circuit. For vehicles equipped with daytime running Lamps (DRL), the FCM electronically steps down the headlamp voltage to provide the desired illumination.

Headlamp Time Delay System
The headlamp time delay system is controlled by the Body Control Module (BCM) via a PCI bus message transmitted by the BCM to the FCM to turn OFF the headlamps.

The headlamp time delay system is activated by turning the headlamps ON (high or low beam) while the engine is running, turning the ignition switch OFF, and then turning the headlamp switch OFF within 45 seconds. The system will not activate if more than 45 seconds elapse between ignition switch OFF and headlamp switch OFF The BCM will allow the headlamps to remain ON for 90 seconds (configurable) before they automatically turn OFF (if the key is in the ignition during the headlamp time delay mode, then both the headlamps and park lamps (including panel dimming) will be ON). Refer to the Owner's Manual for more information.

If the headlamp switch is in the Auto Headlamp Position, the headlamps are ON due to the night signal from the CMTC and the ignition switch is in any position other than run/start, the BCM shall enter a 90 second (configurable) Auto Headlamps time delay mode. If the key is in the ignition during the headlamp time delay mode, then both the headlamps and park lamps (including panel dimming) will be ON. If the key is not in the ignition, then only the headlamps will be ON. The BCM will allow the headlamps to remain ON for 90 seconds before they automatically turn OFF Refer to the Owner's Manual for more information.

Optical Horn/High Beams
When the multi-function switch is pulled to the first detent (optical horn) signal, the headlamps are ON, key-in the ignition the BCM shall send a message via PCI bus to the FCM to turn ON the headlamps drivers to illuminate all four filaments (Low and High beams). When the multi-function switch is pulled to the second detent (high beam) signal and the headlamps are ON, the BCM shall send a message via PCI bus to the FCM to turn ON the headlamps drivers. The High Beams are illuminated and the Low Beams and Fog Lamps (if ON) are extinguished. If the headlamps were in the high beam configuration when power was removed from the headlamps, the headlamps will be configured as low beam the next time they are activated.

WARNING: EYE PROTECTION SHOULD BE USED WHEN SERVICING GLASS COMPONENTS. PERSONAL INJURY CAN RESULT.

CAUTION:
- Do not touch the glass of halogen bulbs with fingers or other possibly oily surface, reduced bulb life will result. Do not use bulbs other than those indicated in the Bulb Application table. Damage to lamp and/or Daytime Running Lamp Module can result. Do not use fuses, circuit breakers or relays having greater amperage value than indicated on the fuse panel or in the Owners Manual.
- Do not use bulbs other than those listed in the Bulb Application Table. Damage to lamp can result. Do not touch halogen bulbs with fingers or other oily surfaces. Bulb life will be reduced.

Fog Lamps
The BCM controls the operation of the fog lamp relay that turns the fog lamps ON and OFF. The Fog lamps can only be ON when the park and low beams are ON. If the high beams are switched ON then the Fog lamps will be automatically turned OFF.

Exterior Lighting Battery Saver
The BCM monitors the status of, and controls, the Park Lamps, Headlamps and Fog Lamp relays. If any exterior lamps are left ON after the ignition is turned OFF the BCM Will turn them OFF after 3 minutes.

HEADLAMP SWITCH
The Headlamp Switch uses a multiplexed (MUX) circuit to the Body Control Module (BCM). The Headlamp Switch controls the Fog lamp relay, Park lamps and the Low and High headlamps. The BCM then sends a signal through the PCI Bus line to the FCM as to what state the switch has selected. The FCM energizes the high side output drivers to turn ON the desired lamps.

PARK LAMP RELAY
The park lamp switch is a direct input to the BCM. The BCM sends a BUS message to the FCM informing it to turn on the park lamp relay. The park lamp relay is then powered through low side control of the FCM. This circuit is electronically controlled and continuously monitored for malfunctions.

FOG LAMP RELAY
The fog lamp switch is a direct input to the BCM. The BCM sends a BUS message to the FCM informing it to turn on the fog lamp relay. The fog lamp relay is then powered through low side control of the FCM. This circuit is electronically controlled and continuously monitored for malfunctions. Fog lamp functionality is not equipped on all vehicles. The FCM "learns" that the vehicle is equipped with fog lamps by reading the BCM BUS message.

BRAKE LAMP SWITCH

Fig.3 Pedal And Brake Lamp Switch:

The brake lamp switch is located under the instrument panel, at the brake pedal arm. It has three internal switches controlling various functions of the vehicle. It's main function is to control operation of the vehicle's brake lamps. Other functions include speed control deactivation, brake sense for the antilock brake system and brake sense for the brake transmission shift interlock.

CAUTION: The switch can only be adjusted once. That is during initial installation of the switch. If the switch is not adjusted properly or has been removed for some service, a new switch must be installed and adjusted.

When the brake pedal is pressed, the plunger on the outside of the brake lamp switch extends outward. This action opens or closes the contacts of the three switches inside the brake lamp switch.

With the brake pedal pressed down (plunger extended), the switch for terminals 1 and 2 is closed completing the circuit. The switch for terminals 3 and 4 is open and so is the switch for terminals 5 and 6.

When the brake pedal is released (plunger pushed in), the three switches assume the opposite positions. The switch for terminals 1 and 2 is now open while the other two switches are now closed, completing their circuits.

A lever on the back of the switch is used to set the switch into the "adjusted" position. A non-adjusted switch will have the lever set to the diagonal position in relation to the switch housing. The plunger can be moved in and out, but the states of the internal switches will not change.

CAUTION: Never move the adjustment lever of the new brake lamp switch without it being properly installed in the vehicle first. Such action will render the switch unusable and the switch must be discarded.

Fig.4 Adjustment Lever Movement:

Once installed in the vehicle as described in the brake lamp switch installation procedure (Refer to ELECTRICAL/LAMPS/LIGHTING - EXTERIOR/ BRAKE LAMP SWITCH - INSTALLATION), the new switch's adjustment lever is rotated to the adjusted position as indicated. This action locks the plunger to the internal switches. Once in this position the switch is permanently adjusted (or locked) and cannot be readjusted or released even if the lever is moved back.

HEADLAMP LEVELING SWITCH - EXPORT
Some vehicles are equipped with a remote headlamp leveling system. This system allows the driver to adjust the vertical headlamp aim from the interior of the vehicle to compensate for passenger or cargo load.

Fig.15 Headlamp Leveling Switch:

The headlamp leveling switch is located next to the headlamp switch on the instrument panel. If the headlamp leveling switch is faulty or damaged, the headlamp switch must be replaced.

MULTI-FUNCTION SWITCH
Turn Signal System
The turn signals are actuated with a lever on Multi-Function Switch, located on the left side of the steering wheel. The signals are automatically turned OFF by a canceling cam (two lobes molded to the clock spring mechanism). The cam comes in contact with the cancel actuator on the turn signal (multi-function) switch assembly. Either cam lobe, pushing on the cancel actuator, returns the switch to the OFF position. The multi-function switch is a resistive MUX switch that feeds inputs to the BCM.

Lane change signaling is actuated by applying partial turn signal stalk movement toward the direction desired until the indicator lamps flashes in the instrument cluster. When the switch stalk is released the stalk will spring back into the neutral position turning OFF the turn signal.

With the ignition switch ON and the turn signal switch stalk actuated left or right, current flows through the:
- Multi-function switch
- Body Control Module
- Integrated Power Module (IPM)
- Turn indicator lamp
- Front and rear turn signal bulbs.

A chime will sound after the vehicle has traveled a distance of approximately 1.0 mile and a speed of 15 mph, with the turn signal ON.

REAR FOG LAMP - EXPORT
The rear fog lamps are incorporated into the tail lamp unit (Refer to ELECTRICAL/LAMPS/ LIGHTING EXTERIOR/TAIL LAMP - REMOVAL) for service procedures.