Volt

Exterior Lighting Systems Description and Operation

The exterior lighting system consist of the following lamps if equipped:

The headlamps consist of one single bulb which provides dipped and main beam. The body control module (BCM) controls the headlamps based on the inputs of the headlamp switch. When a dipped beam request is received, the BCM supplies a B+ to the dipped beam headlamps, illuminating the dipped beam headlamps. When a main beam request is received, the BCM grounds the headlamp main beam relay control circuit.

When the dipped beam headlamps are on and the indicator/multifunction switch is momentarily placed in the flash to pass position, ground is applied to the indicator/multifunction switch. The indicator/multifunction switch applies ground to the BCM through the flash to pass switch signal circuit. The BCM then applies ground to the main beam relay control circuit. This energises the main beam relay, closing the switch side contacts of the main beam relay, applying battery voltage to the left and right main beam fuses. Battery voltage is applied from the main beam fuses through the main beam voltage supply circuit to the main beam headlamp assemblies. This causes the main beam headlamps to illuminate at full brightness momentarily or until the flash to pass switch is released.

The front fog lamp switch signal circuit is grounded momentarily by pressing the front fog lamp switch. The body control module (BCM) energises the front fog lamp relay by applying ground to the front fog lamp relay control circuit. When the front fog lamp relay is energised, the relay switch contacts close and battery voltage is applied through the front fog lamp fuse to the front fog lamp supply voltage circuit which illuminates the front fog lamps.

The rear fog lamp switch signal circuit is grounded through a resistor momentarily by pressing the rear fog lamp switch. The body control module (BCM) energises the rear fog lamp supply voltage circuit which illuminates the rear fog lamp. With the rear fog lamp switch activated the BCM sends a message via serial data to the instrument cluster requesting the instrument cluster to illuminate the rear fog indicator.

The sidelights, tail lamps and number plate lights are turned ON when the headlamp switch is placed in the SIDELIGHT or DIPPED BEAM position or anytime the headlamps are requested. When the BCM receives a request from the headlamp switch to turn ON the sidelights the BCM a sends out a PWM signal, which illuminates the sidelights, tail lamps and number plate lights.

Ground is applied at all times to the indicator/multifunction switch. The indicator lamps may only be activated with the ignition switch in the ON or START position. When the indicator/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the BCM through either the right or left indicator switch signal circuit. The BCM then applies a pulsating voltage to the front and rear indicator lamps through their respective voltage supply circuits. When a indicator request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective indicator indicator be pulsed ON and OFF.

The repeater lamps are located in the front wing. The repeater lamps are used as additional indicator lamps, and operate as described in the Indicator/Hazard Flasher Lamps description.

The hazard flashers may be activated in any power mode. The hazard switch is permanently grounded. When the hazard switch is placed in the ON position, ground is applied through the hazard switch signal circuit to the BCM. The BCM supplies battery voltage to all indicator lamps in an ON and OFF duty cycle. When the hazard switch is activated, the BCM sends a serial data message to the instrument cluster requesting both indicator indicators to be cycled ON and OFF.

The brake pedal position (BPP) sensor is used to sense the action of the driver application of the brake pedal. The BPP sensor provides an analogue voltage signal that will increase as the brake pedal is applied. The BCM provides a low reference signal and a 5 V reference voltage to the BPP sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the brake lamp control circuit and centre high mounted brake lamp control circuit. When the control circuit is energised the brake lamps are illuminated.

When the transmission is placed in the reverse position, the engine control module (ECM) sends a serial data message to the BCM. The message indicates that the gear selector is in the reverse position. The BCM applies battery voltage to the reverse lamps. The reverse lamps are permanently grounded. Once the driver moves the gear selector out of the reverse position, a message is sent by the ECM via serial data requesting the BCM to remove battery voltage from the reverse lamp control circuit.

To provide battery run down protection, the exterior lamps will be deactivated automatically under certain conditions. The BCM monitors the state of the headlamp switch. If the sidelight or headlamp switch is ON when the ignition switch is placed in either the CRANK or RUN position and then placed in the OFF position, the BCM initiates a 10 min timer. At the end of the 10 min, the BCM will turn off the control power output to the sidelight and headlamp relay coils, deactivating the exterior lamps. This feature will be cancelled if any power mode other than OFF becomes active. The BCM will disable battery run down protection if any of the following conditions exist. The sidelight or headlamp switch is placed in the ON to OFF position, and back to the ON position during battery run down protection. The BCM determined that the park or headlamp switch was not active when the ignition was turned OFF.