Lighting Systems: Other Chevrolet Silverado 1500 HD

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 I/P backlighting based on the position of the I/P 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 I/P 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 I/P dimmer switch is in the FULL BRIGHT position.

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

Dimming Input: The scan tool displays the voltage value indicating the position of the I/P 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 I/P 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 I/P 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.

Indicator Dimming: The scan tool displays the duty cycle of the pulse width modulated (PWM) signal distributed by the BCM to the PWM controlled I/P backlighting based on the position of the I/P 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 I/P 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 I/P 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.

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.

Front Fog Lamp Switch: The scan tool the front fog lamp switch. The scan tool displays ACTIVE or INACTIVE when the switch is depressed. The BCM uses this data in controlling the operation of the front fog lamps.

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.

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 Accessory: The scan tool displays the position of the ignition switch. The scan tool displays On when the ignition switch is in the ACCY 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.

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 park lamp switch. The scan tool displays ON when the park lamp switch is in the ON position. The BCM uses this data in controlling the operation of the park lamps.

Outputs

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.

Low Beams: The scan tool displays the commanded state of the low beam relay. The scan tool displays ON when the BCM allows the high beam relay to go to activate the low beam headlamps.

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 activate the park lamps.

Dimming Level: The scan tool displays the commanded state of the interior dimmable lamps. The scan tool displays a percentage based on the position of the thumb wheel.

Daytime Running Lamps: The scan tool displays the commanded state of the daytime running lamps (DRL). The scan tool displays ON when the BCM allows the DRL relay to activate the DRL.

Output Control

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.

Daytime Running lamps: The scan tool displays the commanded state of the daytime running lamps (DRL). The scan tool displays On when the BCM illuminates the DRL.

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 318

Intermittent

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

Headlamp Aiming

The screen method is preferred for aiming headlamps. If the headlamp is equipped with aiming pads, headlamp aiming may be performed using the alternate procedure.

Headlamp aiming is done with the vehicle's low beam lamps. The high beam lamps will be correctly aimed if the low beam lamps are aimed properly. If the high beam needs adjustment, follow the screen method using the high beam bulb as the reference for measurements.

Screen Method for Headlamp Aiming (Visual Aim)

Headlamp aim should be checked

Scheme 319

1. When a new headlamp capsule is installed
2. If service or repairs to the front end area have (or may have) disturbed the headlamps or their mounting
3. The area will consist of a level surface large enough to allow for a vehicle and an additional 7.62 m (25 feet) measured from face of lamps to the front of the aiming screen.
4. The screen will be 1.52 m (5 ft) high x 3.66 m (12 ft) wide with a matte white surface well shaded from extraneous light, and properly adjusted to the floor on which the vehicle stands. Provisions may be made for moving the screen so it can be aligned parallel with the vehicle.
5. The screen shall be provided with a fixed vertical centerline, two laterally adjustable vertical tapes, and one vertically adjustable horizontal tape.
6. If a regular commercial aiming screen is not available, the screen may consist of a vertical wall having a clear uninterrupted area approximately 1.83 m (6 ft) high and 3.66 m (12 ft) wide. The surface should be finished with a washable non-gloss white paint.
7. After the aiming screen has been set up in its permanent location, it is necessary to paint a reference line on the floor directly under the lens of the lamps to indicate the proper location of the headlamps when they are being aimed: Distance between headlamps (1) Center line of screen (2) Adjustable vertical pointer (3) Adjustable horizontal tape (4) Diagram of light screen (5) Vertical center line ahead of right headlamp pointer position (6) 7.62 m (25 ft) (7) Car axis (8) Adjustable vertical pointer Horizontal center line of lamps Vertical center line ahead of left headlamp

Prior to aiming the headlamps, the following steps must be taken

Scheme 320

1. Remove any snow, ice or mud from the vehicle.
2. The vehicle must have a full tank of gas.
3. Stop all other work on the vehicle.
4. If any service has been performed on the vehicle, make sure that all of the components are back in their original place.
5. The vehicle must be on a level surface.
6. The vehicle left tires must be aligned with the reference line extending from the screen with the headlamps aligned with the reference line.
7. Do not load any cargo in the vehicle.
8. The vehicle must contain one person or 72.56 kg (160 lb) on the driver's seat.
9. Inflate the tires to the proper pressure.
10. Simulate the vehicle loads if the intended use of the vehicle is for hauling heavy loads or towing a trailer.
11. Rock the vehicle in order to stabilize the suspension.
12. Turn on the headlamps to low beam and observe the left and the top edges of the high intensity zone on the screen. The edges of the high intensity zone should fall within the specifications.

Scheme 321

Scheme 322

1. Open the hood.
2. Measure from the floor to the center of the headlamp bulb. (Some headlamps have an aim dot marked on the headlamp lens).
3. At the screen, measure from the floor and place the horizontal tape at the measured distance.
4. Measure from the reference line on the floor to the left headlamp bulb centerline.
5. At the screen, measure from the reference line and place the vertical tape at the measured distance.
6. Measure from the reference line on the floor to the right headlamp bulb centerline.
7. At the screen, measure from the reference line and place the vertical tape at the measured distance. IMPORTANT: Do not cover the headlamp, this may cause excessive heat build up.
8. Turn on the low beam headlamps and block the light from projecting onto the screen from the passenger side headlamp.
9. Adjust the vertical aim of the headlamps to the specifications required by the state and the local authorities, or as shown in step number 8.
10. Rotate the headlamp adjuster to change the vertical aim of the headlamp.
11. Repeat the aiming procedure for the passenger side headlamp while blocking the light from projecting onto the screen from the driver side headlamp.
12. Close the hood.
13. This illustration represents the visual optics left (VOL) pattern.
14. This illustration represents the visual optics right (VOR) pattern.
15. This illustration represents all headlamps, except the VOL and VOR.
16. This illustration represents the high beam pattern for all headlamps, including VOL and VOR.

Alternate Aiming Procedure

Tools Required

J 25300-203 Composite Headlight Aimer Adapter. See Special Tools and Equipment .

Instructions for use accompany the tool.

This procedure may only be used on headlamps equipped with aiming pads. Adjustment settings are embossed on the headlamp lens. They are typically located near the aiming pads. In some cases, the adjustment settings are located in other areas of the lens. They will be represented by a number followed by the letter V or the letter H.

1. Remove any snow, ice or mud from the vehicle.
2. The vehicle should be fully assembled and all other work stopped while the headlamp aiming is being done.
3. The vehicle should contain cargo or be loaded to represent normal vehicle use.
4. Tires should be properly inflated.
5. Rock the vehicle to stabilize the suspension.
6. Using J 25300-203, adjust the headlamps to the specifications required by state and local authorities.

Scheme 323

1. Disconnect the electrical connector from the fog lamp.
2. Remove the push pin retainers that attach the fog lamp to the bracket.
3. Remove the fog lamp adjuster bolt and spring from the adjuster nut.
4. Remove the fog lamp from the fog lamp bracket.
5. Remove the fog lamp bracket bolts and bracket, as needed.

Fog Lamp Aiming Procedure

The front fog lamps must be aimed for proper illumination of the road. The front fog lamp aim should be checked when a new front fog lamp assembly is installed, or if service or repairs in the front end area may have disturbed the front fog lamp mounting.

Preparation Procedure

Scheme 324

Scheme 325

1. Park the vehicle on a level surface 7.6 m (25 ft) away from a wall or other flat surface.
2. Measure the distance from the floor to the center of the fog lamp (5).
3. Using this measurement, mark the horizontal centerline of the fog lamp (1) on the flat surface directly in front of the vehicle.
4. Turn ON the fog lamps.
5. Reach under the rear lower edge of the front fascia in order to access the fog lamp vertical adjustment screw on the rear of the fog lamp.
6. Adjust the fog lamp so that the top edge of the fog lamp beam pattern is 100 mm (4 in) below the horizontal centerline.
7. Turn OFF the fog lamps.

Scheme 326

1. Ensure the headlamp switch is in the OFF position.
2. Remove the headlamp. Refer to «Headlamp Assembly Or Headlamp Bulb Replacement (Old Style)»(ref-189006-S14743166122005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style GMC)»(ref-189006-S28917149302005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style Chevy)»(ref-189006-S02985835882005091300000) .
3. Remove the park/turn signal lamp assembly by pushing on the inboard retainer clip.
4. Disconnect the electrical connector from the assembly.

Scheme 327

1. Install the electrical connector to the park/turn signal lamp assembly.
2. Install the lamp assembly.
3. Install the headlamp. Refer to «Headlamp Assembly Or Headlamp Bulb Replacement (Old Style)»(ref-189006-S14743166122005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style Gmc)»(ref-189006-S28917149302005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style Chevy)»(ref-189006-S02985835882005091300000) .

Scheme 328

1. Ensure the headlamp switch is in the OFF position.
2. Remove the headlamp. Refer to «Headlamp Assembly Or Headlamp Bulb Replacement (Old Style)»(ref-189006-S14743166122005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style GMC)»(ref-189006-S28917149302005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style Chevy)»(ref-189006-S02985835882005091300000) .
3. Remove the park/turn signal lamp assembly by pushing on the inboard retainer clip (1).
4. Disconnect the electrical connector from the assembly.
5. Remove the lamp assembly from the vehicle.

Scheme 329

1. Install the electrical connector to the park/turn signal lamp assembly.
2. Align the lamp assembly to the vehicle.
3. Secure the retaining clip by pushing inward on the lamp assembly.
4. Install the headlamp. Refer to «Headlamp Assembly Or Headlamp Bulb Replacement (Old Style)»(ref-189006-S14743166122005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style GMC)»(ref-189006-S28917149302005091300000) or «Headlamp Assembly Or Headlamp Bulb Replacement (New Style Chevy)»(ref-189006-S02985835882005091300000) .

Scheme 330

1. Remove the screws from the roof marker lamp lens.
2. Remove the roof marker lamp lens.
3. Disconnect the electrical connector from the roof marker lamp.
4. Remove the lamp assembly.

Scheme 331

1. Install the lamp assembly.
2. Connect the electrical connector to the roof marker lamp.
3. Install the roof marker lamp lens. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
4. Install the screws to the roof marker lens. Tighten Tighten the screws to 1.9 N.m (17 lb in).

Scheme 332

1. Remove the screws from the roof marker lamp lens.
2. Remove the roof marker lamp lens.
3. Disconnect the electrical connector from the roof marker lamp.
4. Remove the lamp assembly.

Scheme 333

1. Install the lamp assembly.
2. Connect the electrical connector to the roof marker lamp.
3. Install the roof marker lens. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
4. Install the screws to the roof marker lamp lens. Tighten Tighten screws to 1.9 N.m (17 lb ft).

Scheme 334

1. Remove the screws from the roof marker lamp lens.
2. Remove the roof marker lamp lens.
3. Remove the bulb.

Scheme 335

1. In order to install the bulb, push in the bulb until the bulb is seated.
2. Install the roof marker lamp lens. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
3. Install the screws to the roof marker lamp lens. Tighten Tighten the screws to 1.9 N.m (17 lb ft).

Scheme 336

1. Remove the screws from the roof marker lamp lens.
2. Remove the roof marker lamp lens.
3. Remove the bulb.

Scheme 337

1. In order to install the bulb, push in the bulb until the bulb is seated.
2. Install the roof marker lamp lens. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
3. Install the screws to the roof marker lamp lens. Tighten Tighten the screws to 1.9 N.m (17 lb ft).

Scheme 338

1. Ensure the headlamp switch is in the OFF position.
2. Remove the high mounted stop lamp screws.
3. Remove the high mounted stop lamp from the vehicle.
4. Disconnect the electrical connector.

Scheme 339

1. Connect the electrical connector.
2. Install the high mounted stop lamp to the vehicle. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
3. Install the high mounted stop lamp screws. Tighten Tighten the high mounted stop lamp screws to 2 N.m (17 lb ft).
4. Inspect the operation.

Scheme 340

1. Ensure the headlamp switch is in the OFF position.
2. Remove the lens from the lamp assembly (2).
3. Remove the bulb.

Scheme 341

1. Install the bulb.
2. Install the lens to the lamp assembly (2).
3. Install the wiring (3) to the back of the lens assembly.

Scheme 342

1. Ensure that the headlamp switch is in the OFF position.
2. Lower the end gate.
3. Remove the 2 screws retaining the tail/turn signal lamp assembly to the body.
4. Identify the bulb in need of replacement. The top bulb is a parking lamp and stop lamp The center bulb is a turn indicator lamp The lower bulb is a backup lamp
5. Turn the socket assembly.
6. Remove the socket assembly from the housing.

Scheme 343

Scheme 344

1. Turn the socket.
2. Lock the socket in place.
3. Install the tail/turn signal lamp assembly to the vehicle with the 2 screws.
4. Close the endgate.
5. Inspect the operation.

Scheme 345

1. Ensure the headlamp switch is in the OFF position.
2. Lower the endgate.
3. Remove the screws retaining the tail/turn signal lamp assembly to the body.
4. Identify the bulb in need of replacement.
5. Turn the socket assembly and remove the bulb from the housing.

Scheme 346

1. Install the bulb into the socket.
2. Install the socket into the housing turning the socket to lock it in place.
3. Turn the socket and lock in place. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
4. Install the tail/turn signal lamp assembly to the vehicle with the screws. Tighten Tighten the tail/turn signal lamp screws to 2 N.m (18 lb in).
5. Close the endgate.
6. Inspect the operation.

Exterior Lamps

The exterior lighting system consist of the following lamps

1. The Headlamps
2. The Daytime Running Lamps (DRL)
3. Fog Lamps
4. The Park, Tail and Marker Lamps
5. Exterior Courtesy Lamps
6. The Turn Signal/Hazard Lamps
7. The Stop Lamps
8. The Backup Lamps
9. The Clearance Lamps
10. The Roof Beacon Lamp

Headlamps

The headlamps may be turned on in two different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or headlamps operation in low light conditions.

Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the headlamp switch on input circuit when the headlamp switch is in the HEAD position. When the headlamp switch is in the AUTO position, the BCM determines headlamps ON/OFF by the voltage from the ambient light sensor.

If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlight approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.

The high beam indicator is illuminated when the instrument cluster receives a class 2 serial data message from the BCM that the high beams are illuminated.

High Beams

The high beam headlamps receive voltage from the headlamp high relay located in the underhood fuse block. The BCM controls the relay on the headlamp high beam relay control circuit. High beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is grounded, the BCM grounds the headlamp high beam relay control circuit, illuminating the high beam relay control circuit, illuminating the high beam headlamps. The right and left high beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G104.

Low Beams

The low beam headlamps receive voltage from the headlamp low relay located in the underhood fuse block. The BCM controls the relay on the headlamp low beam relay control circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is open, the BCM grounds the headlamp low beam relay control circuit, illuminating the low beam headlamps. The right and left low beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G104.

Daytime Running Lamps (DRL)

The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position, and the headlamp switch is in the AUTO position. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate. 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) or the headlamps for auto headlamp operation. Any function or condition that turns on the headlights will cancel the daytime running lamps operation. The DRL are separate lamps independent of the headlamps. With the headlight switch in the AUTO position, the DRL will either be turned ON or OFF, after an approximate 8 second delay depending on whether daylight or low light conditions are sensed. The DRL 10 A fuse in the underhood fuse block supplies battery positive voltage to the DRL relay switch contacts and relay coil. When the BCM energizes the DRL relay, the DRL receive voltage on the DRL supply voltage circuit. Ground for the DRL is at G100.

Fog Lamps

With both the ignition switch in the [RUN] position, and the park lamps ON, the fog lights will illuminate when the driver depresses the fog lamp switch. The FOG LPS 15 A fuse in the underhood fuse block supplies battery positive voltage to the fog lamp relay switch and coil. With the headlamp switch in either the park or headlamp position, and the fog lamp switch is in the ON position, the body control module (BCM) will energize the fog lamp relay control circuit. The BCM receives the park lamp ON signal from the interior park lamps supply voltage signal circuit. The current flow is from the fog lamp relay to both front fog lamps and to ground G100. The state of the fog lamps will remain the same until the fog lamp switch position is changed, 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 lamps are controlled in much the same way, however the front fog lamps must be on in order to turn on the rear fog lamps. The SEO 1 15 A fuse in the underhood fuse block supplies battery positive voltage to the rear fog lamp relay switch and coil. Both the relay control and current flow are the same as the front fog lamps with the exception of the rear fog lamp ground at G402.

Park, Tail and Marker Lamps

The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in the PARK or HEAD position or anytime the headlights are requested. The underhood fuse 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 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 FR PRK 10 A fuse, RR PRK 10 A fuse, LR PARK 10 A fuse, and the TRL PRK 10 A fuse, and to their respective park and marker lamps. The front park and marker lamps are grounded at G100. The rear park and marker lamps are grounded at G401. The license lamps are grounded at G410. If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the park, tail and marker lamps approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the park, tail and marker lamps will remain on until turned off or the battery runs dead.

Exterior Courtesy Lamps

The BCM, drivers door module (DDM), and the passenger door module (PDM) communicate through the class 2 serial data system. The DDM and the PDM supply power and ground to the left and right exterior lamps respectively. When the BCM commands illuminated entry, a command is also sent to the DDM/PDM for illumination of the exterior courtesy lamps. If the door locks are activated to the LOCK position, or if the ignition switch is turned to either the ON or RUN position the exterior courtesy lamps will deactivate immediately.

When an outside door handle is lifted or a door is opened, the exterior courtesy lamps illuminate.

Turn Signal/Hazard Lamps

The IGN E 10 A fuse in the underhood fuse block supplies battery positive voltage to the turn signal/hazard switch assembly. The FLASH 25 A fuse in the IP fuse block supplies battery positive voltage to the turn signal/flasher module and ground is supplied at G200. When the turn signal switch is placed in either the left or right position, a voltage signal is completed from the turn signal switch to the turn sign/flasher module. When the hazard flasher switch is activated, a ground signal is completed from the turn signal/hazard switch to the turn sign/flasher module. The turn sign/flasher module then sends an on-off voltage signal through the LT TRLR, RT TRLR, LT TURN or RT TURN 10 A fuses in the IP fuse block to the appropriate turn signal or to all 4 fuses for hazard operation. The instrument panel cluster (IPC) indicators receive voltage from the LT TURN and RT TURN fuses as well as the DDM/PDM for the mirror turn signals. The DDM/PDM has no function or control of the mirror turn signals other that a pass through connection for the circuits. The audio chime is also activated when the turn signals are on. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G100. The rear turn signals are grounded at G401. The mirror turn signals are grounded by the DDM/PDM.

Stop Lamps

The STOP LP 25 A fuse in the underhood fuse 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 STOP 15 A fuse and the CHMSL 10 A fuse in the IP fuse block, and to the turn signal/hazard module. The turn signal/hazard module then supplies voltage to both of the trailer rear turn/stop lamp supply voltage circuits.

The voltage from the CHMSL 10 A fuse is to the center high mounted stop lamp (CHMSL) and the trailer jumper harness. The voltage from the STOP 15 A fuse is to the stop lamps, throttle actuator control (TAC) module, and the cruise control.

Backup Lamps

The B/U LP 20 A fuse in the underhood fuse block supplies battery positive voltage to the normally open park neutral position (PNP) switch or backup lamp switch. When driver places the gear selector lever is in the REVERSE position, the switch closes and the voltage is from the switch to the body control module (BCM). The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic day/night mirror. The backup lamps are grounded at G401.

For trailer wiring, a separate backup lamp circuit is connected through the underhood fuse block from the TRLR B/U 10 A fuse to the trailer wiring harness.

Clearance Lamps

The clearance lamps, are turned on when the headlamp switch is placed in the PARK or HEAD position or anytime the headlamps are requested. The underhood fuse 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 INT PRK 10 A fuse, and to the clearance and roof lamps. If the headlamp switch is left in the ON position, the inadvertent power control feature will turn off the park, tail and clearance lamps approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlamp switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the park, tail and marker lamps will remain on until turned off or the battery runs dead.

Roof Beacon Lamp

The roof beacon lamp will illuminate when the driver depresses the roof beacon lamp switch. The SEO B1 15A fuse in the underhood fuse block supplies battery positive voltage to the roof beacon switch. The SEO B2 30A fuse in the underhood fuse block supplies battery positive voltage to the roof beacon relay. When the switch is depressed, the roof beacon coil is energized and the roof beacon relay supplies voltage to the roof beacon lights. The roof beacon relay and roof beacon light is grounded at G304 except crewcab, and crewcab is grounded at G305.

Interior Lamps

The interior lighting consist of the following 2 groups.

This first group includes lamps that may not be dimmed.

1. Courtesy/illuminated entry lamps
2. Dome lamps
3. I/P compartment lamp
4. Map lamps
5. Reading lamps
6. Vanity mirror lamps

Courtesy/Illuminated Entry Lamps

The courtesy/illuminated entry 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, the courtesy/illuminated entry lamps will be disabled. If an outside door handle is lifted or a door is opened, the courtesy/illuminated entry lamps illuminate. After all the doors have been closed the courtesy/illuminated entry lamps will remain illuminated approximately 15 seconds. The courtesy/illuminated entry lamps will also turn on prior to any door being opened, and remain illuminated approximately 40 seconds when the driver removes the ignition key.

The left and right front door courtesy lamps are controlled, and receive voltage and ground from the drivers door module (DDM) and the passenger door module (PDM) respectively. The BCM, DDM, and the PDM communicate through class II serial data for the lamp illumination commands and the door ajar switches.

The remaining courtesy lamps are controlled and receive voltage from the BCM. Ground is provided to the footwell lamps and all courtesy/reading lamps at G203. Ground is provided to the right middle and right rear door at G306. Ground is provided to the left middle and left rear door at G302.

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 activate the interior lamps. The courtesy lamps will remain on, approximately 15 seconds after the door is closed. The BCM will then turn them off through the theater dimming feature. 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, trunk or presses the panic button, the BCM will keep the courtesy lamps on approximately 40 seconds. When the driver uses the remote function actuator transmitter to lock the doors, the BCM will keep the courtesy lamps on approximately 2 seconds. 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 approximately 40 seconds, after an alarm event is completed.

Vanity 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. Ground is provided to the vanity lamps at G203.

IP Compartment Lamp

The inadvertent power courtesy lamps supply voltage circuit of the BCM provides battery positive voltage to the instrument panel compartment lamp. When the IP compartment is opened, a switch closes to provide a ground circuit and the IP compartment lamp illuminates. Ground is provided to the IP compartment lamp at G203.

Reading Lamps

The inadvertent power courtesy lamps supply voltage circuit of the BCM provides battery positive voltage to the reading lamps. The reading lamps and switch are integral to the courtesy/reading lamp assembly. When the switch is closed, voltage is supplied and the lamp illuminates. Ground is provided to the reading lamps at G203.

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, I/P compartment lamp, underhood lamp, 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 incandescent lamps.

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. 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.

1. The instrument panel cluster (IPC)
2. Radio
3. Window and heated seat switches
4. Garage door opener switch
5. Sunroof switch
6. HVAC control assembly
7. Headlamp and panel dimmer switch
8. Tow/haul switch
9. Transfer case shift control switch
10. Height control switch
11. PSIR disable switch
12. PRNDL lamps
13. Traction control switch
14. Steering wheel control switches
15. Rear wiper/washer switch

The left and right front door switch illumination is controlled, receives voltage and ground from the drivers door module (DDM) and the passenger door module (PDM) respectively. The radio is also a class II module and has full control of its illumination. The BCM, DDM, PDM, and radio communicate through class II serial data for the lamp illumination commands.

The I/P cluster illumination lamps receive voltage and are controlled by the BCM on the instrument panel lamps dimming supply voltage circuit. Ground for the instrument panel lamps is at G203.

The various switches, HVAC control assembly, and the PRNDL lamps receive voltage and are controlled by the BCM on the instrument panel lamps dimming control circuit. Ground for the rear window switches is at G302 and G306. Ground for the traction control switch, steering wheel controls, and the rear window/wiper switch is at G108. Ground for the remaining switches is at G203.

1. Traction control switch traction control OFF indicator
2. Height control switch high clearance indicator
3. Transfer case control switch 4WD position indicator
4. Headlamp and panel dimmer switch Headlamp ON indicator
5. Headlamp and panel dimmer switch DRL OFF indicator

The indicators receive voltage from the BCM on the LED dimming circuit. Ground/control for the indicators is from the various modules. The modules controlling the above indicators are as follows

1. Electronic brake control module (EBCM)
2. Electronic suspension control module
3. Transfer case shift control module
4. Body control module (BCM)

Scheme 347