The exterior lighting system consists of the following lamps:

The low beam headlamps may be turned ON in 3 different ways:

Headlamps ON/OFF operation is determined by the position of the headlamp switch and controlled by the body control module (BCM). When the headlamp switch is in the AUTO position, the BCM determines headlamps ON/OFF by the voltage signal from the ambient light sensor.

High intensity discharge (HID) headlamps do not have filaments like the traditional headlamp bulbs. Instead a ballast and an arc tube is used.

When the headlamp switch is placed in the HEAD position, ground from G304 is applied through the headlamps ON signal circuit to the body control module (BCM). In response to this signal, the BCM applies ground to the headlamp low beam relay control circuit energizing the LO BEAM PCB Relay. With the relay energized, battery voltage is applied through the switched side of the relay, the LT and RT LO BEAM fuses, and the supply voltage circuits to a ballast located in each headlamp assembly. The ballast is used to increase the input voltage into a higher voltage in order to create an arc between the electrodes in the arc tube illuminating the headlamp. Ground for the left and right headlamps is provided at G104.

The high beam headlamps for this vehicle does not use separate high beam bulbs. Instead it uses a high beam solenoid with a shutter to re-direct the low beam headlamps for high beam use

When the headlamp dimmer switch is placed in the high beam position, ground from G300 is applied through the dimmer switch and the headlamp dimmer switch signal circuit to the BCM signaling the headlamp high beam request. In response to this signal, the BCM applies ground through the high beam relay control circuit energizing the HIGH BEAM PCB Relay. With the high beam relay energized, battery voltage is applied through the switch side of the relay, the left and right high beam fuses, and the high beam supply voltage circuits to the headlamp high beam solenoids re-directing the low beams for high beam operation. At the same time the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator. Ground for the left and right headlamps is provided at G104.

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 (arc tube). The input current during the steady state operation is lower than 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 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. A high watt power level is necessary in order to bring the lamp to a steady state. Within 2 seconds of the arc being established in the bulb, 70 percent of steady state is complete. Within 30 seconds, 100 percent of the steady state is complete.

Bulb failure, end of life occurs when the bulb gets older and becomes unstable. The bulb may begin shutting itself OFF sporadically and unpredictably at first, perhaps only once during a 24 hour period. When the bulb begins shutting itself off occasionally, the ballast will automatically turn the bulb back on again within 0.5 seconds. The ballast will re-strike 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 excessive, repetitive current input. Repetitive and excessive restarts or re-strikes, without time for the ballast to cool down, will permanently damage the ballast. As a safeguard, when repetitive re-strikes are detected, the ballast will not attempt to re-strike 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 excessive, repetitive bulb re-strikes. When excessive, repetitive bulb re-strikes 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. Bulb failure can be determined if the problem progressively gets worse over the next 100 hours of operation.

HID headlamps have 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 HID at the end of the normal range may appear considerably different in color from one at the other end of the range. A difference in color is normal. Replace the arc tube only if the arc tube is determined to be at the bulb failure stage.

The front turn signal lamps are used for DRL operation. The DRLs will operate only when the engine is running and the headlamp switch is in the AUTO position. When the DRLs are ON, no other exterior lamps such as the parking lamps, tail lamps, etc. will be ON. Also, the instrument panel will not be illuminated.

DRL operation is determined by the ambient light sensor and the controlled by the body control module (BCM). The ambient light sensor is a light-sensitive transistor used to monitor outside lighting conditions. The BCM provides a 5-volt reference signal to the sensor while ground is provided at G300. The sensor will vary this voltage signal between 0.2 and 4.9 volts depending on outside lighting conditions. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either DRL or headlamp operation. When the BCM determines the conditions are met for DRL operation, it turns ON the front turn signal lamps in a steady non-flashing mode. Any function or condition that turns on the headlamps will cancel DRL operation.

When the BCM detects low light conditions, it will turn OFF the daytime running lamps and turn ON the low beam headlamps as described above in Low Beam Headlamp Operation. The BCM will also turn ON the low beam headlamps in daylight conditions when the windshield wipers are turned ON.

When the low beam headlamps are ON and turn signal/multifunction switch handle is pulled toward the driver, ground from G300 is applied through the FTP switch and the flash to pass switch signal circuit to the BCM signaling the flash to pass request. The BCM then turns ON the high beam headlamps as described above, until the turn signal/multifunction switch handle is released. If the low beam headlamps were ON during FTP operation, they will remain ON.

IntelliBeam is an enhancement to your vehicles headlamp system. Using a digital light sensor on the rearview mirror, the system will turn the vehicles high beam headlamps ON and OFF according to surrounding traffic conditions. The IntelliBeam system will turn ON the high-beam headlamps when it is dark enough, there is no other traffic present, and the IntelliBeam system is enabled. When the conditions are met, the inside rearview mirror will send a GMLAN serial data message to the BCM requesting high beam headlamp operation.

Driving with IntelliBeam

IntelliBeam will only activate the high-beams when driving over 32 km/h (20 mph). The high beam headlamps will remain ON, under the automatic control of IntelliBeam, until any of the following situations occur:

The high beam headlamps may need to manually disabled or canceled by turning the low beam headlamps ON, if any of the above conditions exist.

Disabling and Resetting IntelliBeam at the Rearview Mirror

IntelliBeam can be disabled by using the controls on the inside rearview mirror.

AUTO (On/Off)

To disable the system, press this button on the inside rearview mirror. The IntelliBeam indicator will turn OFF and then will not come back ON until the IntelliBeam button is pressed again.

Stalk Disable

When IntelliBeam has turned ON the high-beams, pull or push the high-beam stalk. This will disable IntelliBeam. The IntelliBeam indicator on the mirror will turn OFF. To re-enable IntelliBeam, press the IntelliBeam button on the mirror. A different sensitivity setting is available for dealer diagnostics. This is done by pushing and holding this button for 20 seconds until the IntelliBeam indicator light flashes 3 times.

When the fog lamp switch is turned ON, ground from G304 is applied through the fog lamp switch signal circuit to the body control module (BCM) indicating the fog lamps ON request. In response to this signal, the BCM applies ground to the fog lamp relay control circuit energizing the FOG LAMP PCB Relay. With the relay energized, battery voltage is applied through the switch side of the relay, the FOG fuse, and the fog lamp supply voltage circuits illuminating the fog lamps. At the same time the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) requesting that the fog lamp indicator be illuminated. Ground for the left and right fog lamps is provided at G104.

The park, tail, license, and marker lamps are turned ON when the headlamp switch is placed in either the HEAD or PARK lamp positions, or anytime the automatic light control (ALC) turns the headlamps ON. When the headlamp switch is placed in the park lamp or headlamp positions, ground from G304 is applied through the signal circuit to the BCM indicating the park lamp request. In response to this signal, the BCM applies ground through the park lamp relay control circuit energizing the PRK LAMP Relay. With the relay energized, battery voltage is applied through the switch side of the relay, both park lamp fuses, and the supply voltage circuits illuminating the park, tail, marker, and license lamps.

Park, Position, Tail, and License Lamps (Japan, Taiwan, Korea only)

The park, position, tail, and license lamps are turned ON when the headlamp switch is placed in either the HEAD or PARK lamp positions, or anytime the automatic light control (ALC) turns the headlamps ON. When the headlamp switch is placed in the park lamp or headlamp positions, ground from G304 is applied through the switch signal circuit to the BCM indicating the park lamp request. In response to this signal, the BCM applies ground through both park lamp relay control circuits energizing the PRK LAMP Relay and the RT PRK LAMP (EXP) relay. With the PRK LAMP Relay energized, battery voltage is applied through the switch side of the relay, the LT PRK LAMP fuse, and the supply voltage circuit to the left front position lamp, the left tail lamp, and to the switch side of the EXP LIC LAMP (EXP) Relay. With the RT PRK LAMP (EXP) relay energized, battery voltage is applied through the switch side of the relay, the RT PRK LAMP fuse, and the supply voltage circuits to the right front position lamp, the right tail lamp, and to the coil side of the EXP LIC LAMP (EXP) Relay energizing the relay. With the EXP LIC LAMP (EXP) Relay energized, battery voltage from the LT PRK LAMP fuse is applied through the switch side of the relay and the supply voltage circuits illuminating the license lamps.

Ground for the park lamps is supplied as follows:

Battery voltage supplied to the body control module (BCM) from the fuses listed below is used for turn signal and hazard lamp operation.

When the turn signal switch is place in either the LEFT or RIGHT position, ground from G300 is applied through the turn signal switch signal circuit to the BCM indicating the turn signal request. In response to this signal, the BCM applies a pulsating voltage to the front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. At the same time the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) to cycle the appropriate turn signal indicator ON and OFF.

Ground for the turn signal lamps is supplied as follows:

The hazard flashers may be activated in any power mode. When the hazard switch is placed in the ON position, ground from G300 is applied through the hazard switch and the hazard switch signal circuit to the body control module (BCM) indicating the hazard lamps ON request. In response to this signal, the BCM applies a pulsating voltage to all front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. The BCM also sends a GMLAN serial data message to the instrument panel cluster (IPC) to cycle both turn signal indicators ON and OFF.

The left and right cornering lamps are located within the headlamp assemblies. The BCM will illuminate the cornering lamp only during turn signal operation. When the left or right turn signal is turned ON, the BCM grounds the appropriate cornering lamp relay control circuit energizing the LF or RF CRN LAMP PCB RELAY. With the relay energized, battery voltage is applied through the switch side of the relay, the CRN LAMP fuse, and the cornering lamp supply voltage circuit illuminating the cornering lamp until the turn signal is turned OFF.

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a 5-volt reference voltage and low reference to the brake pedal position sensor. The position sensor provides an analog voltage signal back to the BCM that will increase as the brake pedal is applied. When the brake pedal is applied, the BCM will then apply battery voltage to the left and right stop/turn signal lamp supply voltage circuits and the center high mounted stop lamp (CHMSL) supply voltage circuit illuminating the stop lamps. At the same time the BCM applies battery voltage through the signal circuit to the transmission control module (TCM) and the engine control module (ECM) indicating that the brakes are applied.

Stop Lamps (Japan, Taiwan, Korea only)

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a 5-volt reference voltage and low reference to the brake pedal position sensor. The position sensor provides an analog voltage signal back to the BCM that will increase as the brake pedal is applied. When the brake pedal is applied, the BCM will then apply battery voltage to the stop lamp relay control circuit illuminating the center high mounted stop lamp (CHMSL) and energizing the STOP LAMPS (EXP) Relay. With the relay energized, battery voltage from the STOP LAMP (EXP) fuse is applied through the switch side of the relay and the supply voltage circuit illuminating the stop lamps. At the same time the BCM applies battery voltage through the signal circuit to the transmission control module (TCM) and the engine control module (ECM) indicating that the brakes are applied.

Ground for the stop lamps is supplied as follows:

The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.

Battery voltage from the LT TRN/SIG and RT TRN/SIG fuses located in the rear fuse block is also used by the body control module (BCM) for stop lamp operation.

Battery voltage from the CHMSL/BCK-UP fuse located in the rear fuse block is supplied to the body control module (BCM) for backup lamp operation. When the gear selector is placed in to the REVERSE position, the powertrain control module (PCM) sends a GMLAN serial data message to the BCM indicating that the gear selector is in the reverse position. The BCM then applies battery voltage to the backup lamp supply voltage circuit illuminating the left and right backup lamps. Ground for the left backup lamp is provided at G402 and ground for the right backup lamp is provided at G403.

The BCM controls the lighting system through circuits that enable the exterior lamp functions of the park lamps, the head lamps, the fog lamps, and the interior lamps. The BCM opens these enabling circuits 10 minutes after the ignition switch is turned OFF with no lamp switch activity. If the ignition switch is turned to any position other than OFF, or if a lamp switch is activated during this time period, the timer resets for another 10 minutes.