Exterior Lighting

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.

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 time-out 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 time-out is initiated if the ignition is off and the headlamp switch is cycled from off to on (lamp mode).

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 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.