GM Service Manual Online
For 1990-2009 cars only

Interior Lamps

The interior lamps consist of 2 groups. The first group are those lamps which may not be dimmed. The 2nd group include lamps that may be dimmed.

    • Courtesy/illuminated entry lamps
    • Inside rearview mirror lamps
    • Instrument panel (I/P) compartment lamps
    • Underhood lamp
    • Vanity mirror lamps

Courtesy Lamps

The courtesy lamps include the instrument panel courtesy (IPC) lamps, the exterior courtesy lamps, and the rearview mirror lamps. Turn the courtesy lamps ON manually by placing the interior lamp switch in the DOME position, by opening a door or opening the trunk. After all doors have been closed the courtesy lamps will remain illuminated approximately 15 seconds after the last door closes. Courtesy lamps also turn ON prior to any door being opened, and remain illuminated approximately 30 seconds after the driver removes the ignition key.

The CTSY/LAMP fuse supplies battery voltage to the body control module (BCM). The BCM applies battery voltage to the courtesy lamps through the courtesy lamp supply voltage circuit. When any door is opened, the jam switch contacts close and the BCM receives a door-open input. If the BCM receives a door lock or unlock input or a rear hatch open input, the BCM will activate the courtesy lamp supply voltage circuit, providing battery voltage to all of the instrument panel (I/P) courtesy lamps and the rearview mirror lamps. The BCM also provides a class 2 serial data message to the driver door module (DDM) and passenger door module (PDM) to apply battery voltage to the exterior courtesy lamps.

The courtesy lamps will normally turn OFF using the theater dimming feature. The BCM provides a pulse width modulated ground to the courtesy/reading and inside rearview mirror lamps for the theater dimming feature. The BCM turns OFF the courtesy lamps if a door lock command is received after all of the doors are closed, or if the ignition switch is turned to either the ON or RUN position.

The BCM will provide interior lamp illumination in the event that an air bag has been deployed. Upon deployment of the air bag the inflatable restraint sensing and diagnostic module (SDM) will send a class 2 serial data message to the BCM. The BCM will activate the interior lamps approximately 15 seconds after air bag deployment if the Photocell Status is Dark and the ignition is in the ON position. The interior lamps will remain illuminated until there is a change in the power mode.

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 for 15 seconds after the door is closed. The BCM will turn off the courtesy lamps 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 (RFA) transmitter to unlock the doors, release the rear hatch, or press the panic button, the BCM will keep the courtesy lamps ON for 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 turn OFF immediately. The BCM keeps the courtesy lamps on for 40 seconds after an alarm event is completed.

Vanity Lamps

The CTSY/LAMP fuse supplies battery voltage to the body control module (BCM). The BCM applies battery voltage to the vanity lamps through the courtesy lamp supply voltage circuit. When a vanity mirror cover on one of the sunshades is opened, its switch closes providing a ground circuit, and the vanity lamp illuminates.

I/P Compartment Lamp

The CTSY/LAMP fuse supplies battery voltage to the body control module (BCM). The BCM applies battery voltage to the instrument panel (I/P) compartment lamp through the courtesy lamp supply voltage circuit. When the I/P compartment is opened, its switch closes providing a ground circuit, and the I/P compartment lamp illuminates.

Underhood Lamp

The CTSY/LAMP fuse supplies battery voltage to the body control module (BCM). The BCM applies battery voltage to the underhood lamp through the courtesy lamp supply voltage circuit. When the hood is opened, its switch closes providing a ground circuit, and the underhood lamp illuminates.

Interior Lamps Dimming

Interior lamps dimming are lamps that may be dimmed by operating the instrument panel (I/P) dimmer switch. This group consist of the following lamps:

    • Hazard switch
    • Door switches and the window switches
    • Steering wheel controls
    • HVAC control head assembly
    • Ignition switch
    • Radio
    • Rear compartment/fuel door release switch
    • Traction/suspension control switch
    • Power seat switch
    • PRNDL
    • Power folding top switch
    • Fog lamp switch
    • Front and rear fog lamp switch (Export)

When the ignition switch is turned ON, the vacuum fluorescent (VF) displays, for the radio and HVAC control assembly, the incandescent lamps and the pulse width modulation (PWM) lamps turn ON at maximum brightness. When the park lamps are ON and the ambient light sensor indicates low light conditions, all back lighting turn ON at the dimming level indicated by the I/P dimmer switch. At the same time all VF displays dim in order to match the indicated dimming level. When the headlamp switch is placed in the PARK position, the body control module (BCM) energizes the park lamp relay coil control circuit and dims the interior lamps to the dimming level indicated by the I/P dimmer switch. When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all back lighting lamps are provided with a specific voltage. When the I/P dimmer switch is moved from MIN to MAX, all VF displays and all back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch.

The driver may select parade mode by manually turning on the park lamps during daylight conditions.

Driver Controls and Modules

Driver controls include the following components:

    • Emergency flasher switch
    • Fog lamp switch
    • Headlamp dimmer switch
    • Headlamp switch
    • Interior lamp switch
    • Instrument panel (I/P) dimmer switch
    • Stop lamp switch
    • Turn signal switch

Three modules process the inputs and the controls. The ambient light sensor supplies the body control module (BCM) with a signal for daytime conditions and for low light conditions.

    • Ambient light sensor
    • BCM
    • Instrument panel cluster (IPC)

Battery Rundown Protection/Inadvertent Power

To provide battery run down protection, the interior lamps will be deactivated automatically under certain conditions. The body control module (BCM) initiates a 10 minute timer if the interior lamp relay control output is still active, and the ignition switch is in the OFF position. At the end of the designated time, the BCM will deactivate the interior lamp relay, disabling the interior lamps. This feature will be cancelled if any power mode other than OFF becomes active. The BCM will reset the timer if any interior lamp switch is turned ON, a door is opened, or the remote control door lock receiver (RCDLR) module is activated.