Captiva

Exterior Lighting Systems Description and Operation

The exterior lighting system consists of the following lamps:

The headlamps consist of 2 interchangeable single filament bulbs or 2 high intensity discharge (HID) arc tubes and ballast on each side of the vehicle which provide high and low beams.

The headlamps may be turned ON in 2 different ways:

Battery voltage is applied at all times to the coil and switched side of the headlamp dipped beam relay. Ground is applied at all times from ground G201 to the indicator/multifunction switch. When the indicator/multifunction switch is placed in the HEAD position, ground is applied from the indicator/multifunction switch through the headlamps ON signal circuit to the body control module (BCM). The BCM responds by applying ground to the headlamp dipped beam relay control circuit. This energises the headlamp dipped beam relay, closing the switched side and applies battery voltage to the LEFT and RIGHT DIPPED BEAM fuses. Battery voltage is then applied from the fuses, through the dipped beam control circuits to the left and right dipped beam headlamp assemblies illuminating the dipped beam headlamps. Ground for both headlamps is provided at ground G101.

Warning: The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:

Battery voltage is applied at all times to the coil and switched side of the dipped beam relay. Ground is applied at all times to the headlamp switch. When the headlamp switch is placed in the HEAD position, ground is applied from the headlamp switch through the headlamps ON signal circuit to the body control module (BCM). The BCM applies ground to the headlamp dipped beam relay control circuit. This energizes the dipped beam relay coil, closing the switch side contacts, and applies battery voltage to the LEFT and RIGHT DIPPED BEAM fuses. Battery voltage is then applied from the fuses, through the dipped beam voltage supply circuits to the left and right headlamp ballast located in each headlamp assembly. When battery voltage is applied to the headlamp ballast through the dipped beam voltage supply circuits, the ballast charge the starter to start the lamp. High intensity discharge (HID) headlamps do not have filaments like traditional bulbs, instead the starter uses a high voltage transformer to convert the input voltage into a higher voltage. This increased voltage is used in order to create an arc between the electrodes in the bulb.

Run Up Of The Lamp

Each ballast requires higher amperage in order to ensure normal startup and run up of the lamp. Run up is the term used to describe the extra power level given to the bulb. The input current during the steady state operation is lower that the start up amperage. After the lamp receives the strike from the starter and the arc is established, the ballast uses its operating voltage in order to provide the run up power needed in order to keep the lamp ON. The lamp rapidly increases in intensity from a dim glow to a very high-intensity, bright light called a steady state. Within a few seconds of the arc being established in the bulb, the majority of steady state is complete. 100 percent of the steady state is completed shortly there after. A high watt power level is necessary in order to bring the lamp to a steady state in such a short period of time. The high watt power level allows the lamp to meet the SAE light vs. time specification.

When To Change The HID Bulb

Bulb failure and/or end of life occurs when the bulb gets old and becomes unstable. The bulb may begin shutting itself OFF sporadically and unpredictably at first, perhaps only once during a 24 h period. When the bulb begins shutting itself off occasionally, the ballast will automatically turn the bulb back ON again within 0.5 s. The ballast will restrike the bulb so quickly that the bulb may not appear to have shut off. As the bulb ages, the bulb may begin to shut off more frequently, eventually over 30 times per minute. When the bulb begins to shut off more frequently, the ballast receives an extreme amount of repetitive current input. Repetitive and excessive restarts or restrikes, without time for the ballast to cool down, will permanently damage the ballast. As a safeguard, when repetitive restrikes are detected, the ballast will not attempt to restrike the lamp. The ballast then shuts down and the bulb goes out.

The following symptoms are noticeable signs of bulb failure:

Input power to the ballast must be terminated in order to reset the ballasts fault circuitry. In order to terminate the input power to the ballast, turn the lights OFF and back ON again. Turning the lights OFF and back ON again resets all of the fault circuitry within the ballast until the next occurrence of an extreme amount of repetitive bulb restrike. When an extreme amount of repetitive bulb restrikes occur, replace the starter/arc tube assembly. The ballast will begin the start-up process when the starter/arc tube assembly is replaced. Repeatedly resetting the input power can overheat the internal components and cause permanent damage to the ballast. Allow a few minutes of cool-down time in between reset attempts.

Bulb failures are often sporadic at first, and difficult to repeat. Technicians can identify bulb failure by observing if the problem gets progressively worse over the next 100 hours of operation.

Light Color

White light has a different color rating than regular headlamps. The range of white light that is acceptable is broad when compared to halogens. Therefore, some variation in headlight coloring between the right and left headlamp will be normal. One high intensity discharge (HID) at the end of the normal range may appear considerably different in colour from one at the other end of the range. Difference in color is normal. Replace the arc tube only if the arc tube is determined to be at the bulb failure stage.

The following conditions are necessary for ALC mode to activate:

While in automatic lamp control (ALC) mode, the dipped beam headlamps will be OFF during daylight conditions but will turn ON when the ambient light sensor detects low outside light levels. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 V depending on outside lighting conditions. The body control module (BCM) provides a 5 V reference signal to the ambient light sensor. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In low light conditions, the BCM will respond to the signal from the ambient light sensor by applying ground to the headlamp dipped beam relay control circuit. This energises the dipped beam relay, closing the switched side and applies battery voltage to the LEFT and RIGHT DIPPED BEAM fuses. Battery voltage is applied from the dipped beam fuses, through the dipped beam voltage supply circuits to low headlamp assemblies illuminating the dipped beam headlamps.

The Automatic Headlamp Leveling Systems consist of the following components:

The automatic headlamp leveling system automatically maintains the vertical alignment of the headlamps when the vehicle load and driving conditions change. The SI (Sensor Integrated) - ECM receives the sensor signal/vehicle speed signal by analysing the signal. SI-ECM decides the compensation value suitable for the load condition. Also, SI-ECM outputs the required compensation value to levelling device (actuators) by detecting the vehicle slope value. According to the actuator's operation, headlamp beam is automatically controlled.

The following conditions are necessary for the BCM to illuminate the DRL's:

The dipped beam headlamps operate at reduced intensity when in DRL mode. The ground circuit to the switch side of the DRL relay has a resistor in-line to reduce the intensity of the dipped beam headlamps for DRL operation. The body control module (BCM) receives a signal from the ambient light sensor indicating high outside light level. Under daylight conditions the BCM grounds the DRL relay control circuit energizing the DRL relay. The closed relay switch supplies voltage to the dipped beam headlamps which illuminate at reduced intensity. Any function or condition that turns on the headlamps will cancel DRL operation.

Battery positive voltage is applied at all times to both the coil and switch sides of the front fog lamp relay. When the front fog lamp switch is placed in the ON position, ground is applied through the front fog lamp switch signal circuit to the body control module (BCM). The BCM responds by applying ground to the front fog lamp relay control circuit energizing the front fog lamp relay coil. When the front fog lamp relay coil is energized, the relay switch contacts close and battery voltage is applied through the front FOG LAMP fuse to the front fog lamp control circuit which illuminates the front fog lamps. Ground for the front fog lamps is supplied at G101.

The BCM will send a serial data message to the instrument panel cluster (IPC) to enable the front fog lamp indicator. The front fog lamps will deactivate when either the flash-to-pass or the full beam headlamps are turned ON.

Battery positive voltage is applied at all times to both the coil and switch sides of the rear fog lamp relay. When the rear fog lamp switch is placed in the ON position, ground is applied through the rear fog lamp switch signal circuit to the body control module (BCM). The BCM responds by applying ground to the rear fog lamp relay control circuit energizing the rear fog lamp relay coil. When the rear fog lamp relay coil is energized, the relay switch contacts close and battery voltage is applied through the rear FOG LAMP fuse to the rear fog lamp control circuit which illuminates the rear fog lamps located in the left and right rear tail lamps. Ground for the left rear fog lamps is supplied at ground G401 and ground for the right rear fog lamp is supplied at ground G402.

The BCM will send a serial data message to the instrument panel cluster (IPC) to enable the rear fog lamp indicator.

Battery positive voltage is applied at all times to both the coil and switch sides of the PARKING LAMP relay located in the under bonnet fuse block. The turn signal/multifunction switch is suppled with ground at G201 at all times. When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the parking lamp signal circuit to the body control module (BCM). The BCM responds by applying ground to the parking lamp relay control circuit. This energizes the parking lamp relay coil causing the relay switch contacts to close allowing battery voltage to flow through the left and right PARKING LAMP fuses to all of the parking, tail, number plate, and marker lamps.

Ground is applied at all times at ground G201 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 body control module (BCM) through either the right or left indicator switch circuit. The BCM responds to the indicator switch input by applying a pulsating voltage to the front and rear indicator lamps.

The hazard flashers may be activated in any power mode. The hazard switch is located on the radio/HVAC control panel. The hazard switch signal circuit is momentarily grounded when the hazard switch is pressed. The body control module (BCM) supplies battery voltage to all four 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 panel cluster (IPC) requesting both turn signal indicators to be cycled ON and OFF.

The 15 A BRAKE fuse located in the fuse block - under bonnet, supplies battery positive voltage to the normally open brake lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both left and right brake lamp assemblies, the centre high mounted brake lamp (CHMSL), the engine control module (ECM), and the throttle actuator control (TAC) module.

The control function of the brake lamp switch is a normally closed circuit. When the brake pedal is applied, the BCM detects an open circuit and applies current to the brake lamps. If the brake lamp switch were to become disconnected, the BCM detects the open circuit and applies current to the brake lamps. Brake lamps on is the default state for circuit failure.

When the transmission is placed in the REVERSE position, the transmission control module (TCM) sends a serial data message to the body control module (BCM). The message indicates that the gear selector is in the REVERSE position. The BCM applies battery voltage to the reversing lamps, inside rearview mirror, and object detection module. The reversing lamps are permanently grounded at ground G402 for the left and G401 for the right. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the TCM via serial data requesting the BCM to remove battery voltage from the backup lamp control circuit.