Part 2
Exterior Lighting Systems Description and Operation
Exterior Lamps
The exterior lighting system consists of the following features:
* Backup lamps
* Daytime running lamps (DRL)
* Front fog lamps
* Hazard lamps
* Headlamps
* Park, tail, license, and cornering/side marker lamps
* Position lamps (Export)
* Rear fog lamps (Export)
* Repeater lamps
* Stop lamps
* Turn signal lamps
Daytime Running Lamps (DRL) - Norway/Sweden
The daytime running lamps (DRL) consist of the right and left low beam headlamps illuminated continuously and the park lamps. The DRLs will operate when the following conditions are met:
* The ignition is in the RUN or CRANK position.
* The shift lever is out of the PARK position.
* The high and low beam headlamps are OFF.
* The park lamps are OFF.
* The fog lamps are OFF.
* The park brake is not applied.
When conditions for DRL operation exist, the powertrain control module (PCM) sends a message via GMLAN serial data to the instrument panel module (IPM) indicating the transmission has been removed from the PARK position. The ambient light sensor is a light sensitive transistor that varies its voltage signal to the HVAC control module in response to changes to the outside (ambient) light level. When the HVAC control module receives this signal it communicates via GMLAN with the IPM. The IPM either turns ON the DRLs using a reduced output or the low beam headlamps at full intensity for auto headlamp operation. Any function or condition that turns the headlamps ON will cancel the DRLs operation. The DRLs consists of the low beam headlamps. With the headlamp switch in the OFF position, the headlamps will either be turned ON or OFF, after an approximate 8 second delay depending on whether daylight or low light conditions are sensed.
Twilight Sentinel
Twilight sentinel is a driver convenience that controls the exterior lamps in response to changes to the outside, ambient light level. The twilight sentinel will also keep the low beam headlamps and park lamps ON for a pre-selected period of time after the ignition is turned to the OFF position when night time conditions are sensed. The twilight delay is programmable through the driver information center (DIC) for Driver 1 and Driver 2.
* 0 seconds
* 15 seconds
* 30 seconds
* 60 seconds
* 90 seconds
* 120 seconds
* 180 seconds
* 240 seconds
The DIC will enable the park/headlamp delay feature under the following conditions:
* The time delay is programed to 15 seconds or more for the current driver.
* The headlamp switch is in the auto position.
* The automatic headlamp feature has not been canceled.
* The ambient light sensor status is night time.
* The ignition is OFF.
The delay timer starts once the ignition is turned OFF. The lights will not turn OFF until the set time has been completed or the keyless entry system receives a request for door unlock or trunk release.
Front Fog Lamps
With the ignition switch in the ON or START position, the front fog lamps will illuminate when the driver toggles the front fog lamp switch to the ON position. The front fog lamp switch is a momentary switch that requires the driver to briefly place the front fog lamp switch to the ON position and release it. The instrument panel module (IPM) controls the front fog lamp relay coil. When the driver toggles the front fog lamp switch to the ON position, the switch supplies ground to the front fog lamp switch signal circuit of the IPM. In response to this input, the IPM supplies ground to the front fog lamp relay control circuit. The underhood fuse block supplies battery positive voltage to the switch circuit of the front fog lamp relay. Ignition voltage is available to the front fog lamp relay coil when the key is in the RUN or CRANK positions. When the IPM grounds the front fog lamp relay control circuit the relay coil energizes, closing the switch contacts. Current then flows from the fog lamp fuse through the front fog lamp relay switch to both front fog lamps. Both front fog lamps are permanently grounded. The front fog lamps will default to the OFF position upon a key cycle.
The IPM will turn the park lamps ON when the front fog lamps are ON and send a message via GMLAN serial data 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 high beam headlamps are turned ON. For vehicles exported to Japan or any European Country except Norway or Sweden, the front fog lamps will remain illuminated with the operation of the high beam headlamps or flash-to-pass.
Rear Fog Lamps - European
Rear fog lamps are required equipment on some export vehicles. The rear fog lamps are located in the rear deck lid lamp assembly. The rear fog lamps will only operate when the ignition in the RUN or CRANK positions and either the front fog lamps or headlamps are turned ON. When the driver turns the rear fog lamp switch ON, the switch supplies ground to the rear fog lamp switch signal circuit of the instrument panel module (IPM). In response to this input, the IPM sends a message via GMLAN serial data to the rear integration module (RIM). The RIM responds to this message by grounding the rear fog lamp relay control circuit. When the rear fog lamp relay control circuit is grounded, this energizes the rear fog lamp relay coil causing the switch side contacts to close. Supply voltage from the rear fog lamp fuse flows through the rear fog lamp relay switch to the rear fog lamps.. The IPM communicates via GMLAN serial data with the instrument panel cluster (IPC) requesting the rear fog lamp indicator be illuminated. The rear fog lamps will deactivate if the front fog lamps or headlamps are turned OFF, if the ignition is out of the RUN or CRANK position, or if the driver turns the rear fog lamp switch OFF. The rear fog lamps will default to the OFF position upon a key cycle.
Park, Tail, License, and Marker Lamps
The tail, stop, and turn signal functions are performed by the quarter mounted tail lamps. The quarter mounted tail lamps consist of red lenses and light emitting diodes (LED) instead of incandescent bulbs. The tail lamp assemblies wrap around the corners of the vehicle and serve as the rear side marker. The lower portion of each lamp contains reflectors to alert approaching vehicles for night time driving safety. The park, tail, license, and marker lamps are turned ON when the headlamp switch is placed in the park lamp or headlamp position or anytime the headlights are requested. The park lamps are also turned ON with the front fog lamps. When the ignition switch is in the ON position, the instrument panel module (IPM) provides ground to the controlled voltage circuit of the park lamp relay coil. The underhood fuse block supplies battery positive voltage to the switch contacts of the park lamp relay. When the headlamp switch is placed in the park lamp or headlamp positions, the park lamp switch ON signal circuit is provided ground. In response to this signal, the IPM provides ground to the control circuit of the park lamp relay coil, which energizes the relay coil. When the park lamp relay coil is energized, the relay switch contacts close causing current to flow from the park lamp relay to the LIC/Dimming fuse, LT PARK fuse, and to the RT PARK fuse. From these fuses, current flows to the park lamps, license lamps, side marker lamps, and tail lamps. The LIC/dimming fuse supplies battery positive voltage to the license lamps and IPM instrument panel lamp fuse supply voltage circuit for interior lamps dimming. The inadvertent power control feature prevents the park lamps from remaining on more than 10 minutes if left ON. If the park lamps are turned ON after the ignition switch has been turned OFF, or is in the ACCY position, they will remain ON until turned OFF or the battery runs dead.
Position Lamps - European
The position lamps are on export vehicles only. European countries require that side position lamps are activated when the vehicle is parked along the side of the road. This feature utilizes the front and rear park and the side marker lamps. The position lamp function operates only when the key is in the OFF position and the gear selector is in the PARK position. The position lamp function will operate when the turn signal switch is placed in the right turn position for the right side position lamps to illuminate or the left turn position for the left side position lamps to illuminate. Battery positive voltage is supplied to the standing lamp relay coil and switch. Battery positive voltage is supplied through the normally closed relay contacts of the standing lamp relay switch to each position lamp relay coil. Battery positive voltage is supplied to each position lamp relay switch. When the driver places the turn signal lever in the right or left turn position, the turn signal switch grounds the respective position lamp relay control circuit. This energizes the relay coil, closing the switch contacts providing battery voltage to the respective park and side marker lamps. When the gear selector is out of the PARK position, the rear integration module (RIM) grounds the standing lamp relay coil which removes battery positive voltage from each position lamp relay coil.
Stop Lamps
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 analog voltage signal that will increase as the brake pedal is applied. The instrument panel module (IPM) provides a low reference signal and a 5-volt reference voltage to the BPP sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the IPM will apply battery voltage to the center high mounted stop lamp (CHMSL), transmission control module (TCM), engine control module (ECM), and stop lamp relay. When the stop lamp relay receives battery voltage from the IPM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the stop lamps fuse to illuminate the stop lamps. The stop lamps consist of red lenses and light emitting diodes (LED) instead of incandescent bulbs. 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.
Turn Signal Lamps
With the ignition switch in the RUN position, the turn signal lamps will illuminate when the driver places the turn signal switch in the right or left positions. The instrument panel module (IPM) monitors the signal circuit of the turn signal/multifunction switch. The IPM relays the turn signal switch status to the rear integration module (RIM) via the serial data circuit. The RIM uses the status of the turn signal switch to command the turn signals ON and OFF. The RIM controls both front and rear turn signals. The IPM also sends a message via GMLAN to the instrument panel cluster (IPC) to enable the turn signal indicators located in the IPC ON and OFF depending on the position of the turn signal switch. Voltage is supplied to the front and rear turn signals by the RIM. The rear turn signal functions are performed by the quarter mounted tail lamps. The rear turn signal lamps consist of red lenses and light emitting diodes (LED) instead of incandescent bulbs.
Hazard Flasher Lamps
The hazard flashers may be activated in any power mode. The instrument panel module (IPM) monitors the signal circuit of the hazard switch. When the hazard switch is placed in the ON position, the switch contacts close and battery positive voltage from the IPM flows through the hazard switch to ground. The rear integration module (RIM) turn lamp supply voltage circuit is also provided with ground through the hazard switch when the contacts close at ground which in turn illuminates the hazard switch LED. The RIM uses the status of the hazard switch to command the turn signals ON and OFF. The RIM controls both front and rear turn signals. The IPM sends a message via GMLAN to the instrument panel cluster (IPC) to enable both turn signal indicators in an ON and OFF duty cycle when the hazard switch is placed in the ON position. Voltage is supplied to the front and rear turn signals by the RIM.
Repeater Lamps
The repeater lamps are located on the side of the front fender. The repeater lamps are used as additional turn signal lamps, and operate as described in the Turn Signal Lamps description. The repeater lamps are hard wired to their respective front turn signals.
Backup Lamps
The left rear fuse block supplies battery positive voltage through the REVERSE LAMP fuse to the coil and switch terminals of the reverse lamp relay. The instrument panel module (IPM) sends a power mode message to the rear integration module (RIM) indicating that the ignition is in the RUN position. When the driver places the gear selector in the REVERSE position, the powertrain control module (PCM) sends a message via serial data to the RIM. The RIM provides ground to the reverse lamp relay control circuit which energizes the reverse lamp relay coil. With the reverse lamp relay coil energized, the relay switch contacts close and allow battery positive voltage to flow from the REVERSE LAMP fuse through the relay switch to illuminate the backup lamps.
Battery Run Down Protection/Inadvertent Power
To provide battery run down protection, the exterior lamps will be deactivated automatically under certain conditions. The instrument panel module (IPM) monitors the state of the turn signal/multifunction switch. If the park 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 IPM initiates a 10-minute timer. At the end of the 10 minutes, the IPM will turn OFF the control power output to the park and headlamp relay coils, deactivating the exterior lamps. This feature will be cancelled if any power mode other than OFF becomes active. The IPM will disable battery run down protection if any of the following conditions exist. The park or headlamp switch is placed in the ON to OFF position, and back to the ON position during battery run down protection. The IPM determined that the park or headlamp switch was not active when the ignition was turned OFF.