Exterior Lighting

EXTERIOR LIGHTING
The low and high beam headlamps are controlled directly by an output from the Central Timer Module (CTM). The park lamps and fog lamps (on vehicle so equipped) are controlled via external relays that are energized by the CTM. The headlamp switch provides the control signal through the multifunction switch to the CTM, which indicates low or high beam operation.

The Optical Horn (Flash to Pass) feature operates both the high beam and low beam headlamps.

The CTM provides the Headlamp Time Delay feature. To start the delay, turn the ignition Off while the headlamps are ON. Then turn the headlamp switch to the OFF position. This has to be done within 45 seconds of the ignition being turned OFF, The headlamps will remain ON for 60 ± 5 seconds. If during this delay period the headlamp switch is turned ON and then OFF, or ignition switch is turned ON, the delay will be canceled and the headlamps will turn OFF immediately. During the delay period, only the headlamps are turned ON and the park lamps/fog lamps are turned OFF.

The CTM also provides battery protection to avoid wearing down the battery if the customer leaves the park lamps or headlamps ON for extended period of time with the ignition OFF. If the park lamps or headlamps remain ON for more than 5 minutes while the ignition is OFF, the headlamps and park lamps shall be turned OFF and the input causing the lamps to be ON will be ignored until the input is corrected. Once the 5 minute timeout has extinguished the headlamps and park lamps, any change in the ignition switch, door ajar switches, headlamps switch or park lamp switch will reset the 5 minute timer and return the headlamps and park lamps to normal operation. A 15 minute timeout is initiated if the ignition is OFF and the headlamp switch is cycled from OFF to ON (lamp mode).

Exterior Lamps
The exterior lighting system consist of the following components:
- Central Timer Module (CTM)
- Headlamp Switch
- Fog Lamp Relay
- Park Lamp Relay

Vehicles have incandescent lighting on the exterior for illuminating and indicating purposes. Lighting circuits are protected by fuses. Lighting circuits require an overload protected power source, ON/OFF device, lamps and body ground to operate.

The headlamps operate through the headlamp switch which provides a ground signal to the headlamp beam selector in the multi-function switch. The multi-function switch sends a low or high beam signal input to the Central Timer Module (CTM), which provides current to the headlamps.

For park lamps operation the headlamp switch provides a ground signal to the Central Timer Module (CTM), which energizes the park lamp relay. Once the park lamp relay is energized, voltage is provided to the park lamps.

For fog lamps operation the headlamp switch provides a ground signal to the Central Timer Module (CTM) which energizes the fog lamp relay. Once the fog lamp relay is energized, voltage is provided to the fog lamps.

Day Time Running Lights (Headlamps) System, installed on vehicles manufactured for sale in Canada only, illuminate the headlamps when the ignition switch is turned to the ON position and the CTM receives a vehicle-moving signal from the vehicle speed sensor. This provides a constant Headlamps ON condition as long as the vehicle is moving. The lamps are illuminated at less than 50% of normal intensity.

Turn Signal & Hazard Waring System
The turn signal and hazard warning system includes the following major components, which are described in further detail elsewhere in this service information:
- Combination Flasher
- Hazard Warning Switch
- Turn Signal Cancel Cam
- Turn Signal Indicators
- Turn Signal Lamps
- Turn Signal Switch

The turn signal system in this vehicle includes a turn signal warning chime feature. The EMIC monitors the turn signal indicators and sends an electronic chime request message to the Central Timer Module (CTM) over the Programmable Communications Interface (PCI) data bus network if the indicator remains illuminated with the vehicle speed above about 25 km/h (15 mph) for a distance of greater than about 1.6 kilometers (1 mile). (Refer to INSTRUMENT CLUSTER - DESCRIPTION).

The turn signal system operates on battery voltage received on a fused ignition switch output (RUN/ACC) circuit so that the turn signals will only operate with the ignition switch in the ON or Accessory positions. The hazard warning system operates on non- switched battery voltage received on a fused B(+) circuit so that the hazard warning remains operational regardless of the ignition switch position. When the turn signal system is activated, the turn signal switch and the combination flasher will cause the selected turn signal indicator, front park/turn signal lamp, and rear tail/stop/turn signal lamp to flash ON and OFF. When the hazard warning system is activated, the hazard warning switch and the combination flasher will cause both the right side and the left side turn signal indicators, front park/turn signal lamps, and rear tail/stop/turn signal lamps to flash ON and OFF.

In order to provide the turn signal on warning, the ElectroMechanical Instrument Cluster (EMIC) monitors vehicle speed and distance messages received from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus and the hard wired turn signal switch input to the cluster electronic circuit board. If a turn signal remains indicated for a distance of greater than about 1.6 kilometers (1 mile) and the vehicle speed remains greater than about 24 km/h (15 mph), the EMIC generates a chime request message to the Central Timer Module (CTM) over the PCI data bus. The CTM then generates a chime to provide an audible reminder that a turn signal has been left ON. Once the warning chime begins to sound, it will continue until the turn signal is cancelled, until the vehicle speed falls below about 24 km/h (15 mph), or until the ignition switch is turned to the OFF position.

BRAKE LAMP SWITCH
The hard wired circuits of the turn signal and hazard warning system can be diagnosed using conventional diagnostic tools and methods. For proper diagnosis of the turn signal on warning feature, the EMIC, the CTM, and the PCI data bus must be tested using a DRB III scan tool.

CAUTION: The switch can only be adjusted during initial installation. If the switch is not adjusted properly a new switch must be installed.

The brake lamp switch is used for the brake lamp, speed control and brake sensor circuits. The brake lamp circuit is open until the plunger is depressed. The speed control and brake sensor circuits is closed until the plunger is depressed.

Fig.3 Combination Flasher:

COMBINATION FLASHER
The combination flasher is located under the instrument panel just outboard of the steering column opening. The combination flasher is a smart relay that functions as both the turn signal system and the hazard warning system flasher. The combination flasher contains active electronic Integrated Circuitry (IC) elements. This flasher is designed to handle the current flow requirements of the factory-installed lighting. If supplemental lighting is added to the turn signal lamp circuits, such as when towing a trailer with lights, the combination flasher will automatically try to compensate to keep the flash rate the same.

The combination flasher cannot be repaired or adjusted and, if faulty or damaged, it must be replaced.

The combination flasher controls the following inputs and outputs: fused B(+), fused ignition switch output, right turn signal sense, left turn signal sense, hazard flasher signal, brake lamp switch output, and two outputs each for the right and left turn signal circuits. Constant battery voltage is supplied to the flasher so that it can perform the hazard warning function, and ignition switched battery voltage is supplied for the turn signal function. The Integrated Circuit (IC) within the combination flasher contains the logic that controls the flasher operation and the flash rate. The IC receives separate sense ground inputs from the multi-function switch for the hazard flasher, right turn signal, and left turn signal. A special design feature of the combination flasher allows it to "sense" that a turn signal circuit or bulb is not operating, and provide the driver an indication of the condition by flashing the remaining bulbs in the affected circuit at a higher rate.

If the combination flasher is believed to be faulty test the turn signal and hazard warning system. Then replace the combination flasher with a known good unit to confirm system operation. (Refer to LAMPS/LIGHTING - EXTERIOR/ TURN SIGNAL & HAZARD WARNING SYSTEM - DIAGNOSIS AND TESTING).

HEADLAMP SWITCH
The headlamp switch controls the parking lamps, the headlamps, fog lamps,the interior lamps and the instrument cluster illumination. The headlamp switch also contains a rheostat for controlling the illumination level of the instrument cluster lamps.

The headlamp switch closes a path to ground for the Central Timer Module (CTM) when the park or head lamps are on and the driver door ajar switch is closed.The headlamp switch opens the ground path when the headlamp switch is turned OFF. The ground path is also opened when the driver door ajar switch is open.

The headlamp switch cannot be repaired and, if faulty or damaged, it must be replaced. (Refer to HEADLAMP SWITCH - REMOVAL) for the service procedures.

Fig.14 Multi-Function Switch:

MULTIFUNCTION SWITCH
The multi-function switch is secured with screws to the multi-function switch mounting housing on the left side of the steering column..The switch, its mounting provisions, and its electrical connections are all concealed beneath the steering column shrouds.

A single connector connects the switch to the vehicle electrical system.

The multi-function switch supports the following functions and features:
- Continuous Wipe Modes
- Hazard Warning Control
- Headlamp Beam Selection
- Headlamp Optical Horn
- Intermittent Wipe Mode
- Turn Signal Control
- Washer Mode

The multi-function switch cannot be adjusted or repaired. If any function of the switch is faulty, or if the switch is damaged, the entire switch unit must be replaced.
The multi-function switch uses conventionally switched outputs and a variable resistor to control the many functions and features it provides using hard wired circuitry The switch is grounded to the chassis near the left instrument panel end bracket. When the ignition switch is in the Accessory or ON positions, battery voltage is provided through a fused ignition switch output (RUN/ACC) circuit. Following are descriptions of how the multi-function switch operates to control the many functions and features it provides:
- Continuous Wipe Modes - When the control knob of the multi-function switch is rotated to the High or Low positions, the switch provides a battery voltage output directly to the high or low speed brush of the wiper motor. When the control knob is in the Off position, the switch connects the output of the wiper motor park switch to the low speed brush of the wiper motor.
- Hazard Warning Control - The hazard warning push button is pushed down to activate the hazard warning system, and pushed down again to turn the system off. The hazard warning circuitry provides a signal to the hazard warning sense of the combination flasher to activate or deactivate the flasher output to the warning lamps.
- Headlamp Beam Selection - The multi-function switch control stalk is pulled towards the steering wheel past a detent, then released to actuate the headlamp beam selection switch. Each time the control stalk is actuated in this manner, the opposite headlamp mode from what is currently selected will be activated. The headlamp beam selection switch directs a ground signal output from the headlamp switch to the appropriate low beam or high beam sense of the Central Timer Module (CTM). The CTM then controls a hard wired output to activate the selected headlamp beams.
- Headlamp Optical Horn - The left multi-function switch control stalk is pulled towards the steering wheel to just before a detent, to momentarily activate the headlamp high beams. The high beams will remain illuminated until the control stalk is released. The headlamp beam selection switch provides a momentary ground path to the CTM high beam sense.
- Intermittent Wipe Mode - When the multi-function switch control knob is rotated to the Delay position, the switch provides a battery current signal to the Central Timer Module (CTM). If the Delay mode is selected, the control knob can then be rotated to multiple minor detent positions, which actuates a variable resistor within the switch and provides a hard wired output to the CTM that signals the desired delay interval for the intermittent wiper feature.
- Turn Signal Control - The multi-function switch control stalk actuates the turn signal switch. The multi-function switch turn signal circuitry provides a signal to the right or left turn signal sense of the combination flasher to activate or deactivate the flasher output to the proper turn signal lamps.
- Washer Mode - Pushing the control knob on the end of the multi-function switch control stalk towards the steering column provides battery voltage through the washer switch circuitry to provide a washer signal input to the CTM. The CTM then provides a battery current output to operate the washer pump/motor.

TURN SIGNAL CANCEL CAM
The turn signal cancel cam is concealed within the steering column The turn signal cancel cam consists of two lobes on a molded plastic ring that is snapped into the lower hub of the clockspring rotor. The clockspring mechanism provides turn signal cancellation as well as a constant electrical connection between the horn switch, driver airbag, speed control switches, and remote radio switches on the steering wheel and the instrument panel wire harness on the steering column. The housing of the clockspring is secured to the multi-function switch mounting housing on the steering column and remains stationary. The rotor of the clockspring, including the turn signal cancel cam lobes rotate with the steering wheel.

The turn signal cancel cam is serviced as a unit with the clockspring and cannot be repaired. If faulty or damaged, the entire clockspring unit must be replaced. (Refer to CLOCKSPRING - REMOVAL).

When the turn signals are activated, a turn signal cancel actuator is extended from the inside surface of the multi-function switch housing toward the center of the steering column and the turn signal cancel cam. When the steering wheel is rotated, one of the two turn signal cancel cam lobes will contact the turn signal cancel actuator. The cancel actuator latches against the cancel cam rotation in the direction opposite that which is signaled.