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.

    • Courtesy/ Illuminated Entry Lamps
    • The Inside Rearview Mirror Lamps
    • The Vanity Mirror Lamps
    • The IP Compartment Lamps
    • Underhood Lamp

Courtesy Lamps

The courtesy lamps include the instrument panel courtesy lamps, the exterior courtesy lamps, and the rear view 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 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 after the driver removes the ignition key.

The interior lights fuse supplies battery positive voltage to the BCM. The BCM then applies battery positive voltage to the courtesy lamps through the inadvertant power supply circuit. When any door or if the trunk is opened, the jam switch contacts close and the BCM receives a door-open or trunk open input. If the BCM receives a door lock or unlock input or an trunk open input, the BCM will activate the inadvertant power circuit, providing battery positive voltage to all of the IP courtesy lamps and the rearview mirror lamps. The BCM also provides a class 2 message signal to the driver door module and passenger door module to apply battery positive voltage to the exterior courtesy lamps. You may use some of the courtesy lamps as reading lamps by placing the lamp switch in the ON position.

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 rear view 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 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, 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 transmitter to unlock the doors or the trunk or to 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 interior lights fuse supplies battery positive voltage to the BCM. The BCM then applies battery positive voltage to the vanity lamps through the inadvertant power supply circuit. When the vanity mirror cover on the sunshade is opened, its switch closes providing a ground circuit, and the vanity lamp illuminates.

IP Compartment Lamp

The interior lights fuse supplies battery positive voltage to the BCM. The BCM then applies battery positive voltage to the IP compartment lamp through the inadvertant power supply circuit. When the IP compartment is opened, its switch closes providing a ground circuit, and the IP compartment lamp illuminates.

Underhood Lamp

The interior lights fuse supplies battery positive voltage to the BCM. The BCM then applies battery positive voltage to the underhood lamp through the inadvertant power supply circuit. When the underhood is opened, its switch closes providing a ground circuit, and the underhood 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, incandescent lamps and pulse width modulation (PWM) illumination.

    • The Hazard Switch
    • The Door Switches and the Window Switches
    • The Steering Wheel Controls
    • The HVAC Control Head Assembly
    • The Ignition Switch
    • The Radio
    • The Rear Compartment/Fuel Door Release Switch
    • The Traction/Suspension Control Switch
    • The Power Seat Switch
    • The PRNDL
    • The Power Folding Top Switch
    • The Fog Lamp Switch
    • The Front and Rear Fog Lamp Switch (Export)

When the ignition switch is turned to the ON position, the vacuum fluorescent (VF) displays, for radio and HVAC control assembly, the incandescent lamps and the 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 IP 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 BCM energizes the park lamp relay coil control circuit and dims 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 back lighting lamps are provided with a specific voltage. When the IP 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 IP 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:

    • The Emergency Flasher Switch
    • The Fog Lamp Switch
    • The Headlamp Dimmer Switch
    • The Headlamp Switch
    • The Interior Lamp Switch
    • The IP Dimmer Switch
    • The Stop Lamp Switch
    • The Turn Signal Switch

Three modules process the inputs and the controls. The ambient light sensor supplies the BCM with a signal for daytime conditions or for low light conditions.

    • The Ambient Light Sensor
    • The Body Control Module (BCM)
    • The 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.