Lighting Systems: Other Chevrolet TrailBlazer I

Data

Backlight Dimming: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled IP backlighting based on the position of the IP dimmer switch (Thumbwheel). The scan tool displays 0 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the IP dimmer switch is in the FULL DIM position. The scan tool displays approximately 85 percent when either the low beam headlamps or park lamps are activated and the IP dimmer switch is in the FULL BRIGHT position.

Battery 1: The scan tool displays the battery system voltage received by the module.

Battery 2: The scan tool displays the battery system voltage received by the module.

Battery Voltage: The scan tool displays the battery system voltage.

Dimming Input: The scan tool displays the voltage value indicating the position of the IP dimmer switch (thumbwheel). The scan tool displays 4 volts when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the IP dimmer switch is in the FULL DIM position. The scan tool displays 0 volts when either the park lamps or the headlamps are turned ON and the IP dimmer switch is in the FULL BRIGHT position.

Dimming Level: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the interior lighting circuits. The scan tool displays 0 percent when the interior lamps illumination is OFF. The scan tool displays 100 percent when the interior lamp illumination is at full intensity.

Dimming Potentiometer: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled door switch backlighting based on the position of the IP dimmer switch (Thumbwheel). The scan tool displays 0 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the IP dimmer switch is in the FULL DIM position. The scan tool displays 100 percent when either the headlamps or park lamps are activated and the IP dimmer switch is in the FULL BRIGHT position.

Indicator Dimming: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled IP backlighting based on the position of the IP dimmer switch (Thumbwheel). The scan tool displays 1.2 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the IP dimmer switch is in the FULL DIM position. The scan tool displays 100 percent when either the headlamps or park lamps are activated and the IP dimmer switch is in the FULL BRIGHT position.

Light Sensor: The scan tool displays the output voltage of the ambient light sensor based on the intensity of light detected. As the light intensity increases, the sensor displayed voltage decreases. In the LIGHT state, a low voltage (not less than 1.75 volts) is present and the DRL will be ON. In the DARK state, a high voltage (up to 4.9 volts) is present and the headlamps will be ON.

Low Beam Duty Cycle: The scan tool displays the duty cycle percentage of the pulse width modulated (PWM) ground signal controlling the headlamp driver module (HDM). The BCM uses this feature to signal the HDM to operate the low beam headlamps in low beam headlamp mode at full intensity (100 percent) or in DRL mode at a reduced intensity (81 percent).

Memory Switch Backlight: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled memory switch backlight based on the position of the IP dimmer switch (Thumbwheel). The scan tool displays 0 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the IP dimmer switch is in the FULL DIM position. The scan tool displays 35 percent when either the headlamps or park lamps are activated and the IP dimmer switch is in the FULL BRIGHT position.

Mirror Switch Backlight: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled mirror switch backlight based on the position of the IP dimmer switch (Thumbwheel). The scan tool displays 2 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the IP dimmer switch is in the FULL DIM position. The scan tool displays 25 percent when either the headlamps or park lamps are activated and the IP dimmer switch is in the FULL BRIGHT position.

Window Switch Backlight: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled window switch backlight based on the position of the IP dimmer switch (Thumbwheel). The scan tool displays 0 percent when the headlamp switch is in the AUTO position and the daytime running lamps (DRL) are ON or the IP dimmer switch is in the FULL DIM position. The scan tool displays 100 percent when either the headlamps or park lamps are activated and the IP dimmer switch is in the FULL BRIGHT position.

Inputs

Courtesy Lamp Switch: The scan tool displays the position of the courtesy lamp switch. The scan tool displays Active when the switch is turned ON. The BCM uses this data in controlling the operation of the courtesy lamps.

Dimming Enabled: The scan tool displays if the dimming feature of the module is enabled or disabled. The scan tool displays On when the dimming feature of the module is enabled.

Door Ajar Switch: The scan tool displays Off when the applicable door is fully closed or On when the door is open or ajar.

Flash to Pass Switch: The scan tool displays the position of the flash to pass switch. The scan tool displays On when the switch is pulled to activate the high beams momentarily while the switch is held.

Front Fog Lamp Switch: The scan tool displays the position of the front fog lamp switch. The scan tool displays On when the front fog lamp switch is activated with the park lamps or low beam headlamps ON.

Front Wipers Active: The scan tool displays the state of the wiper motor. The scan tool displays Yes when the wipers are in operation after approximately the first 3 cycles of the wiper blades.

Headlamp Switch: The scan tool displays the position of the headlamp switch. The scan tool displays Active when the headlamp switch is in the ON position. The BCM uses this data in controlling the operation of the headlamps.

High Beam Switch: The scan tool displays the position of the high beam switch. The scan tool displays On when the switch is used to activate the high beams.

Ignition 0: The scan tool displays the position of the ignition switch. The scan tool displays On when the ignition switch is in the RUN or CRANK position.

Ignition 1: The scan tool displays the position of the ignition switch. The scan tool displays On when the ignition switch is in the RUN or CRANK position.

Ignition 3: The scan tool displays the position of the ignition switch. The scan tool displays On when the ignition switch is in the RUN position only.

Inadvertent Power Relay: The scan tool displays the state of the inadvertent power battery rundown protection feature of the BCM. The scan tool displays Off when all inadvertent power circuits are functioning normally.

Interior Lamp Defeat Switch: The scan tool displays the position of the courtesy/dome lamp override switch. The scan tool displays On when the switch is activated requesting the BCM to override the normal interior lamp activation inputs and deactivate the interior lighting.

Key in Ignition: The scan tool displays Yes when the key has been inserted into the ignition switch. The scan tool displays No after the key has been removed.

Left Rear Door Ajar Switch: The scan tool displays Off when the left rear door is fully closed or On when the left rear door is open or ajar.

Liftgate Ajar Switch: The scan tool displays Closed when the liftgate is fully closed or Ajar when the liftgate is open or ajar.

Liftglass Ajar Switch: The scan tool displays Closed when the liftglass is fully closed or Ajar when the liftglass is open or ajar.

Park Brake Switch: The scan tool displays the position of the park brake pedal. The scan tool displays Set when the park brake is engaged closing the switch. The BCM uses this data in controlling the operation of the park brake indicator, the reminder chime feature and the DRL system.

Park Lamp Switch: The scan tool displays the position of the parklamp switch. The scan tool displays Active when the park lamp switch is in the ON position. The BCM uses this data in controlling the operation of the park lamps.

Rear Fog Lamp Switch: The scan tool displays the position of the rear fog lamp switch. The scan tool displays On when the rear fog lamp switch is activated with the park lamps or low beam headlamps ON.

Right Rear Door Ajar Switch: The scan tool displays Off when the right rear door is fully closed or On when the right rear door is open or ajar.

Output Control

Backup Lamps: The scan tool displays the commanded state of the BCM which directly supplies battery positive voltage to the backup lamps. The scan tool displays On when the BCM activates the backup lamps upon receiving a backup lamp request signal from the backup lamp switch.

Dimming Level: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the interior lighting circuits. The scan tool displays 0 percent when the interior lamps illumination is OFF. The scan tool displays 100 percent when the interior lamp illumination is at full intensity.

High Beams: The scan tool displays the commanded state of the high beam relay. The scan tool displays On when the BCM allows the high beam relay to go to ground activating the high beam headlamps.

Inadvertent Power Relay: The scan tool displays the state of the inadvertent power battery rundown protection feature of the BCM. The scan tool displays Off when all inadvertent power circuits are functioning normally.

Low Beam Duty Cycle: The scan tool displays the commanded state of the headlamp driver module. The BCM displays 100 percent for the low beam headlamps in low beam headlamp mode at full intensity or 81 percent in the DRL mode resulting with a reduced intensity.

Park Lamp Relay: The scan tool displays the commanded state of the park lamp relay. The scan tool displays On when the BCM allows the park lamp relay to go to ground to activate the park lamps.

Scheme 220

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.

Screen Method for Headlamp Aiming

The screen method requires an area set up specifically for headlamp aiming.

The area should consist of a level surface large enough to allow for a vehicle and an additional 7.62 m (25 ft) as measured from the face of the headlamps to the aiming screen.

Scheme 221

The screen should be a wall or other flat surface at least 1.52 m (5 ft) high by 3.66 m (12 ft) wide with a matte white surface well shaded from extraneous light, and 90 degrees to the floor. The screen should be provided with a permanent vertical reference line 0.61 m (2 ft) from the left edge of the screen, 2 laterally adjustable vertical tapes, and one vertically adjustable horizontal tape.

After the aiming screen has been set up and located, paint or tape a reference line on the floor 15.24 m (50 ft) from the vertical reference line on the screen. This line should be perpendicular to the aiming screen and a mark placed at 7.62 m (25 ft) from the screen.

Scheme 222

Scheme 223

Scheme 224

1. Align the left tires of the vehicle with the reference line extending from the screen with the headlamps aligned with the reference line.
2. Remove any snow, ice or mud from the vehicle.
3. The vehicle must be fully assembled and all other work stopped while the headlamp aiming is being done.
4. The vehicle must contain one person or approximately 160 lb (73 kg).
5. Tires should be properly inflated.
6. Rock the vehicle to stabilize the suspension.
7. Measure from the floor to the reference mark on the headlamp lens (2). The graphic shows a GMC headlamp. Chevrolet and Oldsmobile are similar.
8. At the screen, measure from the floor and place the horizontal tape at the above measured distance.
9. Turn the low beam headlamps ON.
10. The graphic shows the vertical (1) adjustment, no horizontal adjustments are required. The graphic shows a GMC headlamp. Chevrolet and Oldsmobile are similar. Adjust the headlamps to the specifications required by state and local authorities.
11. The beam pattern must be positioned as shown in the graphic. IMPORTANT: Do not place a cover directly on the headlamp assembly while the headlamp is ON.
12. Adjust one headlamp at a time while blocking the light from the other. The cover must be away from the headlamp. The following list refers to the callouts in the graphic: The low beam centerline reference mark (4). Distance from ground to the low beam bulb centerline reference mark (1). The ground line (2). Horizontal edge of the low beam headlamp pattern (3). The edge of the headlamp pattern (3), must be 5 cm (2 in) below the reference mark (4), with the vehicle 7.62 m (25 ft) away.

Scheme 225

1. Remove the fog lamp bulb and socket. Refer to «FOG LAMP BULB REPLACEMENT - FRONT»(ref-188868-S38432821512005090300000) .
2. Remove the 3 nuts that retain the fog lamp to the fascia (2).
3. Remove the fog lamp from the fascia.

Scheme 226

1. Install the fog lamp to the fascia (2). NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
2. Install the 3 fog lamp retaining nuts. Tighten Tighten the nuts to 10.0 N.m (88 lb in).
3. Install the fog lamp bulb and socket. Refer to «FOG LAMP BULB REPLACEMENT - FRONT»(ref-188868-S38432821512005090300000) .
4. Aim the fog lamp(s). Refer to «FOG LAMP AIMING PROCEDURE»(ref-188868-S34724286392005090300000) .

Scheme 227

Scheme 228

1. Remove the fog lamp bulb and socket. Refer to «FOG LAMP BULB REPLACEMENT - FRONT»(ref-188868-S38432821512005090300000) . IMPORTANT: The fog lamp bracket is permanently attached to the fascia. Do not remove the fog lamp bracket from the fascia, replace only the fog lamp.
2. Remove the 2 push pins (1) that retain the fog lamp to the fog lamp bracket.
3. Remove the aim adjustment screw (2) from the fog lamp.
4. Remove the fog lamp from the fog lamp bracket.

Scheme 229

Scheme 230

1. Position the fog lamp to the fog lamp bracket.
2. Install the 2 push pins (1) that retain the fog lamp to the fog lamp bracket.
3. Install the aim adjustment screw (2) to the fog lamp.
4. Install the fog lamp bulb and socket. Refer to «FOG LAMP BULB REPLACEMENT - FRONT»(ref-188868-S38432821512005090300000) .
5. Aim the fog lamp(s). Refer to «FOG LAMP AIMING PROCEDURE»(ref-188868-S34724286392005090300000)

Scheme 231

1. Turn the fog lamp switch to the OFF position.
2. Rotate the bulb socket counter clockwise in order to release the socket from the fog lamp housing.
3. Remove the socket from the fog lamp housing (2).
4. Remove the bulb from the socket.

Scheme 232

1. Install the bulb to the socket.
2. Index the tabs on the bulb socket to the slots in the fog lamp housing.
3. Install the socket to the fog lamp housing (2).
4. Rotate the socket clockwise until fully seated.

Fog Lamp Aiming Procedure

Proper road illumination and safety require the fog lamps to be aimed. The front fog lamp aim should be checked when a new front fog lamp assembly is installed, or if any service repairs have been performed to the vehicle which disturb the front fog lamp mounting or the vehicle ride height.

There are no horizontal adjustments for aiming the front fog lamp assemblies on this vehicle.

The front foglamps can be adjusted by turning the adjustment screw (1) located below the backside of the lamp, next to the electrical connector.

Use the following guidelines in order to adjust the aim

Scheme 233

1. Turn the TORX® adjustment screw clockwise in order to raise the aim.
2. Turn the TORX® adjustment screw counter-clockwise in order to lower the aim.

Scheme 234

1. To ensure accurate vertical front fog lamp aiming, first perform the following steps to prepare the vehicle. Make sure that all the components are in place on the vehicle, the tires are properly inflated, and there is not any mud or snow clinging to the vehicle. Stop all other operations of work on the vehicle. Make sure the fuel level is 1/2 full or more. Jounce the vehicle to settle the suspension. Place the vehicle on a level surface 7.6 m (25 ft) from the target screen. Measure the distance from the floor to the center of the fog lamp (5). Using this measurement, mark the horizontal centerline of the fog lamp (1) on the target screen directly in front of the vehicle. Start the vehicle in order to level the suspension.
2. Turn the front fog lamps ON.
3. Access the fog lamp vertical adjuster.
4. Adjust the fog lamp up or down until the top edge of the high intensity zone on the screen is 102 mm (4 in) below (2) the horizontal centerline (1).
5. Turn OFF the front fog lamps.

Scheme 235

1. Open the hood.
2. Remove the headlamp. Refer to «HEADLAMP BULB REPLACEMENT»(ref-188868-S05204017772005090300000) .
3. Rotate the bulb and socket counterclockwise in order to remove the bulb and socket from the housing.
4. Remove the side marker bulb (3) or turn signal/park bulb (4) from the socket.

Scheme 236

1. Install the side marker bulb (3) or turn signal/park bulb (4) to the socket.
2. Wipe the bulb with a clean cloth to ensure the bulb is free of any dirt or oil.
3. Install the bulb and socket to the headlamp by rotating the bulb and socket clockwise, locking the retaining tabs to the headlamp.
4. Install the headlamp. Refer to «HEADLAMP BULB REPLACEMENT»(ref-188868-S05204017772005090300000) .
5. Close the hood.

Scheme 237

1. Open the hood.
2. Remove the headlamp. Refer to «HEADLAMP BULB REPLACEMENT»(ref-188868-S05204017772005090300000) .
3. Rotate the bulb and socket counterclockwise in order to remove the bulb and socket from the housing.
4. Remove the side marker bulb (4) or turn signal/park bulb (3) from the socket.

Scheme 238

1. Install the side marker bulb (4) or turn signal/park bulb (3) to the socket.
2. Wipe the bulb with a clean cloth to ensure the bulb is free of any dirt or oil.
3. Install the bulb and socket to the headlamp by rotating the bulb and socket clockwise, locking the retaining tabs to the headlamp.
4. Install the headlamp. Refer to «HEADLAMP BULB REPLACEMENT»(ref-188868-S05204017772005090300000) .
5. Close the hood.

Scheme 239

1. Open the hood.
2. Remove the headlamp. Refer to «HEADLAMP BULB REPLACEMENT»(ref-188868-S05204017772005090300000) .
3. Rotate the bulb and socket counterclockwise in order to remove the bulb and socket from the housing.
4. Remove the turn signal/park bulb (3) from the socket.

Scheme 240

1. Install the turn signal/park bulb (3) to the socket.
2. Wipe the bulb with a clean cloth to ensure the bulb is free of any dirt or oil.
3. Install the bulb and socket to the headlamp by rotating the bulb and socket clockwise, locking the retaining tabs to the headlamp.
4. Install the headlamp. Refer to «HEADLAMP BULB REPLACEMENT»(ref-188868-S05204017772005090300000) .
5. Close the hood.

Scheme 241

1. Remove the bulb socket from the cornering lamp.
2. Release the forward retaining tab (1) from the fascia.
3. Remove the rearward retaining tab (2) from the fascia.
4. Remove the cornering lamp from the vehicle.

Scheme 242

1. Position the cornering lamp to the fascia.
2. Install the rearward retaining tab (2) to the fascia.
3. Secure the forward retaining tab (1) to the fascia.
4. Install the bulb socket to the cornering lamp.

Scheme 243

1. Push the retaining tab inward and rotate the socket counterclockwise.
2. Remove the socket from the cornering lamp housing (1).
3. Remove the bulb from the socket.

Scheme 244

1. Install the bulb into the socket.
2. Index the socket tabs to the cornering lamp housing slots.
3. Position the socket into the cornering lamp housing (1).
4. Rotate the socket clockwise until the locking tab is fully seated.

Scheme 245

1. Push the retaining tab inward and rotate the socket counterclockwise.
2. Remove the socket from the cornering lamp housing (1).
3. Remove the bulb from the socket.

Scheme 246

1. Install the bulb into the socket.
2. Index the socket tabs to the cornering lamp housing slots.
3. Position the socket into the cornering lamp housing (1).
4. Rotate the socket clockwise until the locking tab is fully seated.

Scheme 247

1. Turn OFF the headlamp switch.
2. Insert a small flat bladed tool under the rear edge of the lens and pry upward.
3. Remove the lens.
4. Twist the bulb counterclockwise to remove.

Scheme 248

1. Insert the bulb into the bulb socket and twist clockwise to install.
2. Insert the forward edge of the lens into the opening and press the rear edge downward to install.

Scheme 249

Scheme 250

1. Open the liftgate.
2. Lower the rear portion of the headliner by releasing the 2 headliner retaining pins.
3. Disconnect the high mount stoplamp electrical connector (2).
4. Remove the grommet (1) from the body NOTE: Do NOT raise the liftgate while the liftgate glass is open. This can result in damage to the high-mounted stoplamp, the liftgate hinges, or the liftgate glass.
5. Close the liftgate.
6. Open the liftgate window.
7. Remove the 2 screws that retain the high mount stoplamp to the lift gate window reveal molding.
8. Remove the high mount stoplamp from the vehicle.

Scheme 251

Scheme 252

1. Install the high mount stoplamp to the lift gate window reveal molding, ensuring the center retaining tab is fully seated. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
2. Install the 2 screws that retain the high mount stoplamp to the lift gate window reveal molding. Tighten Tighten the 2 retaining screws to 2.5 N.m (22 lb in).
3. Close the liftgate window.
4. Open the liftgate.
5. Install the grommet (1) to the body.
6. Connect the high mount stoplamp electrical connector (2).
7. Attach the rear portion of the headliner to the roof panel, by seating the 2 headliner retaining pins.
8. Position the lift gate opening weatherstrip over the headliner.

Scheme 253

1. Remove the backup lamp socket.
2. Remove the 2 nuts that retain the backup lamp to the fascia.
3. Remove the back up lamp from the fascia.

Scheme 254

1. Install the back up lamp to the fascia. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
2. Install the 2 backup lamp retaining nuts. Tighten Tighten the nuts to 10.0 N.m (88 lb in).
3. Install the backup lamp socket.

Scheme 255

1. Push the retaining tab (1) inward and rotate the socket counterclockwise.
2. Remove the socket from the backup lamp housing.
3. Remove the bulb from the socket.

Scheme 256

1. Install the bulb into the socket.
2. Index the socket tabs to the backup lamp housing slots.
3. Position the socket to the backup lamp housing.
4. Rotate the socket clockwise until the retaining tab (1) is fully seated.

Scheme 257

Scheme 258

1. Remove the 2 screws that retain the license lamp lens to the liftgate.
2. Remove the license lamp lens from the liftgate.
3. Remove the bulb (1) from the socket.

Scheme 259

Scheme 260

1. Install the bulb (1) to the socket.
2. Wipe the bulb to ensure the bulb is free of dirt or oil.
3. Position the license lamp lens to the liftgate.
4. Verify that the license lamp lens gasket is fully seated to the liftgate. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
5. Install the 2 license lamp lens retaining screws. Tighten Tighten the screws to 1.4 N.m (12 lb in).

Scheme 261

Scheme 262

1. Remove the 2 screws that retain the tail lamp assembly to the body.
2. Pull the assembly directly rearward in order to release the 2 locking pins.
3. Disconnect the tail lamp electrical connector.
4. Remove the lamp assembly from the vehicle.
5. Remove the 2 socket assembly retaining screws.
6. Simultaneously release the bottom 4 locking tabs and partially remove the socket assembly.
7. Release the top 2 locking tabs and remove the socket assembly from the tail lamp assembly.

Scheme 263

Scheme 264

1. Position the socket assembly to the tail lamp assembly.
2. Hold the top 2 locking tabs apart while pushing the socket assembly into place.
3. Hold the bottom 4 locking tabs apart while pushing the socket assembly into place.
4. Verify that the housing is fully seated with the locking tabs fully seated. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
5. Install the 2 socket assembly retaining screws. Tighten Tighten the screws to 1.9 N.m (17 lb in).
6. Connect the tail lamp electrical connector.
7. Push the tail lamp assembly directly forward in order to seat the 2 locking pins.
8. Install the 2 tail lamp assembly retaining screws. Tighten Tighten the screws to 1.9 N.m (17 lb in).

Scheme 265

1. Remove the tail lamp assembly. Refer to «TAIL LAMP REPLACEMENT»(ref-188868-S25141419102005090300000) .
2. Place the tail lamp assembly onto a clean prepared surface.
3. Pull the bulb straight out in order to remove the tail lamp bulb from the socket assembly.

Scheme 266

1. Install the tail lamp bulb to the socket assembly.
2. Ensure the bulbs are wiped clean and free of any oil or dirt.
3. Install the tail lamp assembly to the vehicle. Refer to «TAIL LAMP REPLACEMENT»(ref-188868-S25141419102005090300000) .
4. Check the bulbs for proper operation.

Scheme 267

Scheme 268

1. Remove the side marker (2) and cornering lamp (1) sockets from the side marker.
2. Release the side marker retaining ear (1) from the fascia.
3. Remove the side marker retaining stem (2) from the fascia.
4. Remove the side marker from the fascia.

Scheme 269

Scheme 270

1. Install the side marker to the fascia.
2. Install the side marker retaining stem (2) to the fascia.
3. Seat the side marker retaining ear (1) to the fascia.
4. Install the side marker (2) and cornering lamp (1) sockets to the side marker.

Exterior Lamps

The exterior lighting system consist of the following lamps

1. The Headlamps
2. The Daytime Running Lamps (DRL)
3. The Clearance Lamps (Y92 roof rack only)
4. The Cornering Lamps
5. The Front Fog Lamps
6. The Rear Fog Lamps (Export)
7. The Park, Tail and Marker Lamps
8. The Turn Signal Lamps
9. The Stop Lamps
10. The Backup Lamps

Headlamps

The headlamp driver module (HDM) is an electronic module that provides electrical power to the vehicle low beam headlamps. The HDM is controlled by a pulse width modulated (PWM) ground signal from the body control module (BCM). The BCM determines the desired lamp intensity using the ambient light sensor, multifunction switch and the park brake switch as inputs. In general, the HDM will operate in 1 of 3 modes

1. Reduced Intensity Mode: This mode is used by features that do not require or allow maximum low beam headlamp intensity such as daytime running lights (DRL) (nominal: 85% duty cycle).
2. Full Intensity Mode: This mode is used by features that require full low beam headlamp intensity such as low beam headlamp operation in manual or auto modes (nominal: 100% duty cycle).
3. Off Mode: This is the default mode of the system that will occur when none of the features described above are active. The BCM will deactivate its PWM output (0% duty cycle) during this mode.

The normal battery voltage input to the HDM must be between 6 and 16 volts DC to operate. Any deviation to these values could cause improper operation.

Major components of this system are the BCM, HDM, ambient light sensor, multifunction switch, park brake switch and low beam headlamps.

The headlamps may be turned on in 3 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, normal operation occurs.

Second, with the headlamp switch is placed in the AUTO position, automatic lamp control (ALC) occurs. During ALC control, the headlamps will be in daytime running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. Third, in wiper activated headlamp (WAH) mode. Only when the wiper system is activated while the vehicle is in gear, the wiper blades have completed at least 3 cycles, and then a 35 second time period expires, will the BCM switch from DRL mode to headlamp mode during daylight conditions. When the gearshift lever is placed in the PARK or NEUTRAL position or if the wipers are turned off, normal manual or ALC operation will resume after approximately 60 seconds.

The HDM and high beam relay receive battery positive voltage directly from the battery. The BCM supplies a 100% duty cycle PWM ground signal to the HDM for automatic headlight control and normal headlight operation. The BCM also supplies ground to the high beam relay coil for high beam headlight operation. When the driver places the headlamp switch in the HEADLAMP position and the dimmer switch is in the low beam position, the HDM switches to full output sending current flow through the left and right low beam headlamp fuses to both low beam headlamps. The dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-Pass (FTP) position from G102 to deactivate the low beam headlights and activate the high beam headlights. With the headlights in the low beam position, the high beams may be momentarily turned on or flashed by activating the FTP portion of the switch.

The instrument panel cluster (IPC) illuminates the high beam indicator when the body control module (BCM) detects that the high beams are requested. The IPC receives a class 2 message from the BCM requesting illumination.

The Headlamps On at Exit and Perimeter Lighting modes can be adjusted using the steering wheel controls to select the desired function as displayed in the driver information center. The Headlamps On at Exit selection will allow the driver to customize the period of time that the headlamps remain illuminated upon exiting the vehicle. This period can be adjusted from 0 seconds to 180 seconds. The Perimeter Lighting feature allows the driver to select if they desire the headlamps and backup lamps to illuminate when the door UNLOCK button on the key fob is activated. This feature can be turned ON or OFF by using the driver information center steering wheel control buttons.

Daytime Running Lamps (DRL)

The ambient light sensor is a light sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes to the outside (ambient) light level. When the BCM receives this signal it will either turn on the daytime running lamps (DRL) through the HDM using the reduced output or the headlamps at full intensity for auto headlamp operation. Any function or condition that turns on the headlights will cancel the daytime running lamps operation. The daytime running lamps (DRL) are the low beam headlights at a reduced intensity. With the headlight switch in the OFF position, the headlights will either be turned ON or OFF, after an approximate 8 second delay depending on whether daylight or low light conditions are sensed. When the BCM signals the HDM for DRL operation in daylight conditions, the HDM illuminates the low beam headlights at a reduced intensity. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position and the parking brake is released. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.

On vehicles equipped with the 4-position headlamp switch, the DRL feature can be temporarily disabled by momentarily placing the headlamp switch in the DRL defeat position. This will signal the BCM to disable the DRL function until the headlamp switch is momentarily placed in the DRL defeat position again or until the next ignition key cycle.

DRL operation in Manual Transmission equipped vehicles will occur when the ignition switch is in the RUN position, and the parking brake is released.

Headlamp Leveling (Export)

The IGN E fuse in the I/P fuse block supplies battery positive voltage to the headlamp leveling switch. When the driver places the headlamp leveling switch in any position, a signal is sent to the headlamp leveling actuators to adjust the headlight aiming to the desired position. The underhood fuse block supplies battery positive voltage and G107 and G103 supplies ground to the headlamp leveling actuators.

Fog Lamps

With both the ignition switch in the RUN position and the park lamps or low beam head lamps on, the fog lights will illuminate when the driver presses the fog lamp switch. The FOG LAMP fuse in the engine wiring harness junction block supplies battery positive voltage to the fog lamp relay. With the headlamp switch in either the park or headlamp position and the fog lamp switch is pressed, the body control module (BCM) will energize the fog lamp relay control circuit. The current flow is from the fog lamp relay to both front fog lamps and to ground G107 and G103. The state of the fog lamps either ON or OFF will remain the same until the fog lamp switch is pressed again, or the ignition switch is cycled OFF and ON. Fog lamp operation will be cancelled whenever the park lamps are turned OFF or the high beam headlights have been selected.

The rear fog lamp (Export) is located in the left tail lamp assembly. The rear fog lamp has a dedicated relay and both the relay control and current flow operate the same as the front fog lamps. The RR FOG fuse supplies voltage to the lamp and G 401 supplies ground.

Park, Tail, Marker, License, and Clearance Lamps

The park, tail, marker, license, and clearance (Y92 only) lamps are turned on when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested. The I/P BATT fuse in the engine wiring harness junction block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned on, the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the individual park lamp circuit fuses and to their respective park, tail, marker, and license lamps. The front park and marker lamps are grounded at G 107 and G 103. The tail lamps are grounded at G401 and G402. The license lamps are grounded at G401. When equipped with the Y92 roof rack option, the clearance lamps are grounded at G302. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, the park, tail, marker, license, and clearance lamps will remain on until turned off or the battery runs dead.

The T PARK fuse in the rear fuse-relay block supplies battery positive voltage to a separate park lamp circuit connected to the trailer wiring harness.

Turn Signal Lamps

The smart flasher (GMSF) is an automotive flasher designed to accept turn, hazard, and brake inputs. The GMSF will provide corresponding outputs to the exterior lamps and instrument panel turn signal indicator lamps. This lighting system has dedicated lamps for the turn/hazard functions and dedicated lamps for the brake function. The system incorporates the use of flash rates for diagnostics. The flash rate is a calculation of the number of flashes that occur within a 60 second period. This system uses a percentage of on-time to off-time called duty cycle. For the bulb outage condition, the indicator of the vehicle side on which the outage occurs shall assume bulb outage flash rate mode. The opposite side indicator will assume the normal flash rate mode for an input from the non bulb outage side of the vehicle. Hazard warning lamp outage will maintain a normal flash rate as long as 2 or more exterior signaling lamps are functional. During all modes of operation, the IPC will receive the same flash rates and duty cycles that the exterior lamps receive.

The IPC will then control the indicators in the cluster. The vehicle operator will be provided with an audible and visual indication of the flasher operation. Below is a table with flash rates and duty cycles

Scheme 271

The IGN E fuse in the engine wiring harness junction block supplies Ignition positive voltage to the turn signal switch assembly. With the ignition switch in the RUN or START position, ignition positive voltage is connected through the turn signal and hazard switch assembly to the GMSF which is powered by the FLASHER fuse also in the engine wiring harness junction block and is grounded at G201. When the turn signal switch is placed in either the left or right position, the circuit is complete from the GMSF to the turn signal lamps and to ground. The GMSF then sends an on-off voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G103 and G107. The rear turn signals are grounded at G401 and G402.

The IPC illuminates the TURN SIGNAL ON indicator in the driver information center when the IPC determines that the turn signal is active for more than 1.2 km (0.75 mile). The IPC also sends a class 2 message to the radio in order to activate the audible warning.

On vehicles equipped with the outside rear view mirror turn signal lamps, the turn signal voltage is also sent to the respective front door module. The door modules then distribute power and ground to the activated lamp.

For trailer wiring, separate turn signal circuits are connected through the GMSF to the trailer wiring harness.

Cornering Lamps

The turn signal switch sends battery positive voltage to the cornering lamps which will constantly remain illuminated until turn signal operation is cancelled. The cornering lamps are grounded at G103 and G107.

Stop Lamps

The STOP fuse in the engine wiring harness junction block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the VEHICLE STOP fuse and the VEHICLE CHMSL fuse. The current flow is now to the stop lamps which are grounded at G401 and G402. The center high mounted stop lamp (CHMSL) is grounded at G401.

For trailer wiring, a separate stop lamp circuit is connected through the GMSF to the trailer wiring harness.

Backup Lamps

On a vehicle equipped with an automatic transmission, the backup lamps request signal is sent from the powertrain control module (PCM) to the body control module (BCM) via class 2. This signal is based on the state of the park neutral position (PNP) switch. On a manual transmission equipped vehicle, the B/U fuse in the engine wiring harness junction block supplies battery positive voltage to the normally open backup lamp switch. When the driver places the gear selector lever is in the REVERSE position, the backup lamp switch closes and the current flow is from the backup lamp switch to the BCM signaling for backup lamp illumination.

The BCM directly supplies voltage for backup lamp operation on both automatic and manual transmission vehicles. The backup lamps are grounded at G401 and G402 (G305 on vehicles that have the backup lamps located in the lower bumper fascia).

For trailer wiring, a separate backup lamp circuit is connected through the TRLR B/U fuse to the trailer wiring harness.

Interior Lamps

The interior lighting consist of the following 2 groups. This first group includes lamps that may not be dimmed.

1. The Cargo lamp
2. The Dome lamps
3. The Reading Lamps
4. The Vanity Mirror Lamps

Courtesy Lamps

The courtesy lamps include the reading lamps, cargo lamp, and dome lamps. The cargo lamp and dome lamps may be manually turned on or off by placing the interior lamp switch in the ON or OFF position. When the driver places the dome lamp defeat switch in the OFF position, these courtesy lamps will be disabled. If a door is opened, the courtesy lamps illuminate. After all the doors have been closed, the courtesy lamps will remain illuminated approximately 15 seconds after the last door closes. The courtesy lamps will also turn on prior to any door being opened and will remain illuminated approximately 40 seconds when the driver removes the ignition key. The BCM will immediately turn off the courtesy lamps if a door lock command is received with all of the doors closed, or if the ignition switch is turned to either the ON or RUN position.

Keyless Entry Interior Illumination

When the driver uses the door key in order to unlock the doors, the body control module (BCM) receives a door unlock signal. The BCM must have inputs that indicate that the ignition switch is OFF, the courtesy lamp switch is OFF and all the doors are closed. The BCM will then illuminate the interior lamps. The courtesy lamps will remain illuminated for approximately 15 seconds after the door is closed. If the door locks are activated to the LOCK position, or if the ignition switch is turned to either the RUN or CRANK position, the courtesy lamps will turn off immediately.

When the driver uses the remote function actuator transmitter to unlock the doors or presses the panic button, the BCM will keep the courtesy lamps on for approximately 15 seconds. If the door locks are activated to the UNLOCK or LOCK position or if the ignition switch is turned to either the RUN or CRANK position, the courtesy lamps will turn off immediately. The BCM will also keep the courtesy lamps on for approximately 40 seconds after an alarm event is completed.

Vanity Mirror Lamps

The inadvertent power courtesy lamps supply voltage circuit of the BCM provides battery positive voltage to each vanity mirror lamp. When the vanity mirror cover on the sunshade is opened, a switch closes to provide a ground circuit and the vanity lamp illuminates.

Battery Rundown Protection/Inadvertent Power

The BCM inadvertent power courtesy lamps supply voltage circuit provides battery positive voltage to all of the interior reading lamps and both visor vanity mirror lamps. In the event that any of these lamps were to remain illuminated for a period of more than 20 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power courtesy lamps supply voltage circuit to prevent a total battery discharge condition. Only when the ignition switch is cycled back to the RUN position will the BCM reset the internal timer and reactivate the inadvertent power courtesy lamps supply voltage circuit.

The BCM also utilizes the inadvertent power courtesy lamps supply voltage circuit as a courtesy lamp request signal circuit when none of the lamps in the circuit are illuminated. When a lamp switch is activated, the BCM receives the request for lamp illumination and switches to supplying voltage to the inadvertent power courtesy lamps supply voltage circuit.

Interior Lamps Dimming

The second group includes lamps which may be dimmed. This group may use a combination of vacuum fluorescent (VF) illumination and of incandescent lamps.

1. Door switches and window switches
2. HVAC control head assembly
3. Radio and steering wheel controls
4. The Rear HVAC/Radio controls
5. The instrument panel cluster (IPC)

When the ignition switch is turned to the RUN position, the radio's vacuum fluorescent (VF) displays turn on at maximum brightness. When the park lamps are on, all incandescent back lighting turn on at the dimming level indicated by the I/P dimmer switch. At the same time all vacuum fluorescent (VF) displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the BCM. When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all incandescent back lighting lamps are provided with a specific voltage. The incandescent back lighting lamps are then grounded at G201, G302, and G303. When the I/P dimmer switch is moved from MIN to MAX, all vacuum fluorescent (VF) displays, as well as all incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch.

Scheme 272