Exterior Lighting
EXTERIOR LAMPSThe 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.
TURN SIGNAL & HAZARD WARNING 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 kilometers per hour (15 miles per hour) for a distance of greater than about 1.6 kilometers (1 mile). (Refer to ELECTRICAL/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 kilometers-per-hour (15 miles-per-hour), 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 kilometers-per-hour (15 miles-per-hour), or until the ignition switch is turned to the Off position.
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 DRBIII scan tool.
Fig.19 Multi-Function Switch:
MULTI-FUNCTION 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 multifunction 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.