GM Service Manual Online
For 1990-2009 cars only

Interior Lamps

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

    • The courtesy/reading lamps
    • The cargo lamp
    • The vanity mirror lamps
    • The IP compartment lamps
    • The instrument panel (IP) courtesy lamps

Courtesy Lamps

The courtesy lamps, include the roof rail/reading lamps, the footwell lamps, dome and rear view mirror lamps. The courtesy lamps, may be manually turned on by placing the interior lamp switch in the DOME position, or by opening a door. 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 remain illuminated approximately 30 seconds when the driver removes the ignition key.

The BCM L fuse in the console fuse block, supplies battery positive voltage to the body control module (BCM). The courtesy lamps supply voltage circuit of the BCM supplies battery positive voltage to all interior courtesy lamps. When any door is opened the door open switch contacts close and a door open input is received by the BCM. If a door lock or unlock input is received by the BCM, it will activate the inadvertent power relay inside of the BCM, providing battery positive voltage to all interior courtesy lamps. Some of the courtesy lamps may also be used as reading lamps by placing the lamps switch in the ON or OFF position.

The courtesy lamps will normally turn off using the theater dimming feature. The BCM provides a pulse width modulated ground to all courtesy/reading, dome and inside rear view mirror lamps for the theater dimming feature. The BCM will immediately turn off the courtesy lamps if a door lock command is received with all the doors closed, or if the ignition switch is turned to either the ON or RUN position.

The courtesy lamps will also turn on after an air bag deployment for approximately 15 seconds.

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 30 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 approximately 40 seconds, after an alarm event is completed.

Vanity Lamps

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

IP Compartment Lamp

The courtesy lamps supply voltage circuit also provides battery positive voltage to the instrument panel compartment lamp. When the IP compartment is opened, its switch closes to provide a ground circuit and the IP compartment lamp illuminates.

Cargo Lamp

The courtesy lamps supply voltage circuit also provides battery positive voltage to the cargo lamp. When the rear compartment is opened, its switch closes to provide a ground circuit and the cargo lamp illuminates.

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.

    • The door switches and the window switches
    • The HVAC control head assembly
    • The radio
    • The instrument panel cluster (IPC)
    • The steering wheel controls
    • The heated seat switch
    • The HUD switch
    • The lift glass window release switch and traction control switch

When the ignition switch is turned to the ON position, the vacuum fluorescent (VF) displays (radio and HVAC control assembly), incandescent lamps, turn on at maximum brightness. When the park lamps are on and the ambient light sensor indicates low light conditions, all incandescent back lighting turn on at the dimming level indicated by the IP dimmer switch. At the same time all vacuum fluorescent (VF) displays dim to match the indicated dimming level. The BCM L fuse in the console fuse block, supplies battery positive voltage to the BCM. The I/P courtesy lamps supply voltage circuit of the BCM, supplies battery positive voltage to all the dimmable lamps. When the headlamp switch is placed in the PARK position, the BCM will then dim the interior lamps to the dimming level indicated by the IP dimmer switch. When the driver selects a dimming setting by moving, the IP dimming switch potentiometer, all incandescent back lighting lamps are provided with a specific voltage. The incandescent back lighting lamps are then grounded at G200, G301 and G302. When the IP 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 IP dimmer switch.

The driver may select parade mode by manually turning on the park lamps during daylight conditions. The front park lamp circuit supplies voltage to the instrument panel cluster, radio and HVAC assembly for a park lamp on input, and the displays will become full bright.

Battery Rundown Protection / Inadvertent Power

The body control module (BCM) controls the lighting system through circuits that enable both the exterior lamp functions of the park lamps, the headlamps , and the fog lamps, as well as the interior lamps. The BCM opens these enabling circuits 20 minutes after the ignition switch is turned OFF with no lamp switch activity. If the ignition switch is turned to any position other than OFF, or if a lamp switch is activated during this 20-minute period, the timer resets for another 20 minutes.