GM Service Manual Online
For 1990-2009 cars only

Exterior Lamps

The exterior lighting system consists of the following lamps:

    • The headlamps
    • The daytime running lamps (DRL)
    • The park/turn signal lamps
    • The front side marker lamps
    • The hazard lamps
    • The tail lamps
    • The stop lamps and center high-mounted stop lamp
    • The backup lamps
    • The license plate lamps

Headlamps

All models are equipped with composite headlamps. Each composite headlamp consists of 1 halogen bulb, providing both high and low-beam operation, and a headlamp assembly. The bulb is separate from the assembly. The headlamp assembly does not need to be removed from the vehicle in order to replace the bulb. It is not necessary to re-aim the headlamps when replacing only the bulb.

The turn signal/headlamp switch lever is located on the left side of the steering column. The switch lever controls both the low-beam and high-beam headlamp operations. The lever is only serviceable as part of the combination switch. For combination switch removal and installation procedures, refer to Inflatable Restraint Steering Wheel Module Coil Replacement in SIR. A twist type knob on the end of the switch lever controls the operation of the parking lamps and the headlamps. A solid tone will sound as a reminder if you open the drivers door with the key out of the ignition and the park lamps or the headlamps on. When either the parking lamps or headlamps are activated, the following also illuminate:

    • The tail lamps
    • The side marker lamps
    • The rear license plate lamps
    • The instrument cluster assembly lamps
    • The heater control unit lamp
    • The radio lamp
    • The cigar lighter lamp
    • The IP ashtray lamp
    • The manual selector lever lamp

The TAIL fuse applies voltage to the coil and the contacts in the tail lamp relay at all times. With the turn signal/headlamp switch lever in the park lamp or headlamp position, the coil is provided a ground through the turn signal/headlamp switch to G200. When the ambient light sensor senses a low light condition, a path to ground is provided to the coil through the sensor to G200. When the coil energizes, the contacts in the tail relay close and voltage is applied to the lamps mentioned above. All of the lamps illuminate because the lamps are grounded permanently.

Low Beam System Operation

The headlamps may be turned on two different ways. First, when the ignition switch is turned to the ON position, voltage is applied to the ambient light sensor through the DEF Fuse. The ambient light sensor permanently grounds to G200. When the ambient light sensor senses a low light condition, a path to ground is provided to the coil of the headlamp relay through the ambient light sensor. This same signal is also provided to the DRL control module and disables DRL operation. Voltage is provided from the H/L Fuses, through the DRL diode to the coil of the headlamp relay. The relay contacts close providing a ground to the headlamps. The headlamps illuminate at full intensity. Second, when the end of the of the turn signal/headlamp switch lever is turned to the second detent position, the headlamps illuminate.

The daytime running lamps (DRL) control module and the turn signal/headlamp switch control the headlamps. The H/L, L and H/L, R Fuses supply voltage to the headlamps, the high beam indicator and the headlamp relay through the DRL diode at all times. With the switch in the HEAD position and the dimmer switch in low, ground is provided to the low beam filaments through the dimmer switch and the closed contacts of the Headlamp Relay to G200. The low beam filaments illuminate when the ground is supplied.

High Beam System Operation

The high-beam headlamp operation is controlled using the turn signal/headlamp switch lever on the steering column. In order to change headlamp operation from low-beam to high-beam, push the switch lever toward the instrument panel until the detent is felt and release. With the switch lever in the high position, the high beam filaments in the headlamps ground through the dimmer switch, through the closed contacts of the headlamp relay to G200. The high beam filaments will light when the ground is supplied. The high-beam indicator-blue in the instrument cluster will light during high-beam headlamp operation. The ground path for the high beam indicator is the same as the high beam filaments. In order to change headlamp operation back to low-beam operation, pull the turn signal switch lever toward the driver until the detent is felt and release.

Flash-to-Pass System Operation

The Flash-to-Pass feature allows the driver to signal the driver of another vehicle of his intention to pass. This is achieved by pulling the lever toward the driver, which will cause the high beam operation to illuminate until the lever is released. The flash-to-pass feature will function with the switch lever in either the OFF, the parklamp, or the low-beam headlamp setting.

With the dimmer switch in the pass position, the high beam filaments in the headlamps ground through the dimmer switch to G200. The high beam filaments will light with ground supplied. The ground path for the high beam indicator is the same as the high beam filaments.

Daytime Running Lamps (DRL)

Daytime running lamps (DRL) are standard equipment on all models. Operating through the low beams at 80 percent intensity of the normal output, the DRL system operates under the following conditions:

    • When the engine is running.
    • When the parking brake is not applied.
    • When the turn signal/headlamp switch lever is in either the OFF or the park lamp position.
    • When the ambient light sensor senses a bright light condition.

The DRL control module receives voltage through the IG fuse when the ignition switch is in the ON or START position and is permanently grounded at G200.

The following will prevent DRL operation:

    • When the parking brake is engaged, the parking brake switch closes, providing a ground to the DRL control module, disabling the DRL operation.
    • When the generator is not running, a switch in the generator closes, providing a ground to the DRL control module, disabling the DRL operation.
    • When the turn signal/headlamp switch is in the headlamp position, providing a ground to the DRL control module, disabling the DRL operation.

When all of the conditions for DRL operation are met, the DRL control module provides a ground for the low beam filaments in the headlamps through the DRL control module to G200. The H/L, L and H/L, R Fuses supply the voltage to the headlamps at all times. The low beam filaments will light at 80 percent intensity.

Park/Turn Signal Lamps

The front park/turn signal lamps are integrated into the headlamp assemblies. The front lamp lens is clear. It contains one amber double filament bulb. The rear turn signal lamps are integrated into the tail lamp. An amber lens covers the rear turn signal lamp. It contains one clear single filament bulb. The turn signal/headlamp switch lever is located on the left side of the steering column. Turn the end of the switch lever to the first detent position in order to turn on the park lamps. The parking lamp filament illuminates when either the parking lamps or headlamps are activated.

When a turn is signaled, the appropriate front park lamp and rear turn signal lamp flashes to signal a turn. The turn signals operate only with the ignition switch in the ON position and will not operate during hazard flasher operation. When making a partial turn, such as when changing lanes, the driver has the option of moving the lever to a detent stop. The turn signal lamps and the turn signal indicator will continue to flash as long as the lever is held in this position and will cancel automatically when the lever is released. The detent position allows a lane change or shallow turn to be made without failing to cancel the turn signal lamp. Moving the lever past the detent position to its furthest upward or downward position will provide conventional turn signal operation. Turn signal operation is controlled by the turn/hazard signal flasher that is located on the back of the junction block and the turn signal/headlamp switch lever. With the ignition switch in the ON or the START position, voltage applies through the TURN fuse and the normally closed contacts of the hazard switch and the turn/hazard flasher to the turn switch. When the switch lever is moved to the left turn position, voltage applies to the left turn indicator in the instrument cluster, the left front turn signal lamp, and the left rear turn signal lamp. The lamps are ground permanently. The lamps light immediately and start to flash 80-90 times a minute while the solid state timing unit in the turn/hazard flasher operates.

The lamps operate similarly when the switch lever is moved to the right turn position.

The turn signal lever is only serviceable as part of the combination switch. For combination switch removal and installation procedures, refer to Inflatable Restraint Steering Wheel Module Coil Replacement in SIR.

Front Side Marker Lamps


Object Number: 487809  Size: SH

The front side marker lamps (1) are mounted in the front bumper fascia. Each lamp consists of a single filament bulb covered by amber colored lenses. They are operational any time the parking lamps or headlamps are activated.

Hazard Lamps

The hazard switch is in the center of the instrument panel to the right of the instrument panel cluster. The hazard switch controls the operation of the hazard lamp circuit. Press the hazard switch in order to cause the turn/hazard flasher to disengage the turn signal circuit. This will engage the hazard lamp circuit. Voltage applies at all times through the HAZ fuse to the normally open contacts of the hazard switch. With the hazard switch pressed, the contacts close. When the contacts close voltage applies through the turn/hazard flasher, back through the hazard switch, to the following components:

    • The turn indicators in the instrument panel cluster
    • The front turn signal lamps
    • The rear turn signal lamps

The lamps are ground permanently. The lamps light immediately and start to flash 80-90 times a minute while the solid state timing unit in the turn/hazard flasher operates. The turn/hazard flasher is located on the back of the junction block. The junction block is located beneath the left side of the instrument panel and is mounted to the left front side door hinge pillar. The hazard lamp circuit operates regardless of the position of the ignition switch.

Press the hazard switch again in order to disengage the hazard lamp circuit. This returns the turn/hazard flasher to the turn signal mode.

Refer to Hazard and Turn Signal Flasher Replacement for turn/hazard flasher removal and installation procedures.

Tail Lamps

The tail lamps are located on the vehicle body at each side of the endgate on 2-door models or the rear door on 4-door models. Each tail lamp consists of the following:

    • A clear single filament turn signal bulb
    • A clear single filament backup lamp bulb
    • A clear double filament stop/tail lamp bulb

The tail lamp lens is multi colored. A red lens covers the stop lamp, an amber lens covers the turn signal lamp and a clear lens covers the backup lamp.

Stop lamps and Center High-Mounted Stop lamp

The high-mounted stop lamp contains 1 bulb on 2-door models and attaches to the top of the endgate. The high-mounted stop lamp contains 5 bulbs on 4-door models and is located at the top of the rear door window.

Each of the tail lamps also contains a double filament stop lamp bulb. The stop lamp filament lights under the following conditions:

    • The stop lamp switch is closed. The stop lamp is designed to operate in conjunction with the tail lamps whenever the brake pedal is depressed.
    • The parking lamps are activated.
    • The headlamps are activated.

Voltage applies at all times through the STOP fuse to the normally open contacts of the stop lamp switch. When the brake pedal is depressed, the contact in the stop lamp switch close. The voltage applies to the tail/stop lamps in the left and right tail lamps and the center high-mounted stop lamp. The lamps are grounded to G400 and G401. The stop lamps will operate even with the tail lamps on.

Backup Lamps

The backup lamps are incorporated into the tail lamps. The backup lamps operate with the ignition switch in the ON position. Placing the transmission in the reverse (R) position closes the backup lamps circuit and turns the backup lamps on. Voltage applies through the TURN fuse to one of the following components:

    • The backup lamp switch on manual transmissions.
    • The park/neutral position (PNP) switch on 3-speed automatic transmissions.
    • The transmission range switch on 4-speed automatic transmissions.

The voltage applies to the backup lamps in the tail lamps. Since the tail lamps are ground permanently at G400, the lamps will light.

License Plate Lamps

There are 2 license plate lamps located in the rear license plate housing directly over the license plate. Each license plate lamp contains 1 clear, single filament bulb. The license plate lamp bulb filament illuminates when either the parking lamps or the headlamps are activated.