GM Service Manual Online
For 1990-2009 cars only

Interior Lighting

The interior lighting consist of lamps that may not be dimmed (Interior Lamps) and lamps that may be dimmed (Interior Lamps Dimming).

Interior Lamps

The first group of lamps are the interior lamps, which includes the lamps that may not be dimmed manually:

    • The IP compartment lamp
    • The foot well courtesy lamps
    • The inside rear view mirror lamps
    • The ignition switch illumination bulb
    • The courtesy lamp rear compartment
    • The roof rail courtesy lamps
    • The vanity mirror lamps

Interior Lamps Features

The interior lamps system features the following functions:

    • An illuminated entry feature that illuminates the courtesy lamps when entering the vehicle or activating the remote keyless entry system.
    • An illuminated exit feature that illuminates the courtesy lamps when the ignition key has been removed from the ignition.
    • An inadvertent power feature that supplies voltage to all interior lamps after the ignition is turned OFF. The inadvertent power feature will deactivate all interior lamps after 20 minutes to prevent battery rundown.
    • A theater dimming feature that will slowly dim the interior lamps from full brightness to off.
    • A dimmer switch that illuminates the courtesy lamps.
    • Individual switches for control of each interior lamp that is not illuminate with the interior lamp switch.

Courtesy/Illuminated Entry Lamps

When the body control module (BCM) is in an active state (awake) it energizes the courtesy lamps supply voltage circuit. The courtesy lamps supply voltage circuit supplies voltage to all of the interior lamps, including the illuminated entry lamps (courtesy lamps). The illuminated entry lamps are turned on when they receive a ground from the interior lamp control circuit of the BCM. When the ignition is in the LOCK position the BCM will energizes the interior lamp control circuit under the following conditions:

    • A door open signal circuit transitions to an active state, opening a door
    • The door handle switch signal circuit transitions to an active state
    • The use of the remote keyless entry (RKE) to unlock the side doors

When the courtesy lamps supply voltage circuit and the interior lamp control circuit are active the courtesy/illuminated entry lamps will illuminate. The courtesy lamps/illuminated entry lamps include the following interior lamps :

    • The roof rail courtesy lamps
    • The ignition illumination bulb
    • The I/P courtesy lamps
    • The inside rear view mirror

When the driver uses the remote function actuator transmitter to unlock the doors, the BCM will illuminate the courtesy lamps for approximately 40 seconds, unless another BCM function causes the lamps to remain active. If the ignition switch is turned to either the RUN or START position the courtesy lamps will turn off immediately.

When a door open signal is active with the ignition in the OFF position the BCM will illuminate the courtesy lamps for approximately 25 seconds, unless another BCM function causes the lamps to remain active. If the ignition switch is turned to either the RUN or START position the courtesy lamps will turn off immediately.

Courtesy/Illuminated Exit

The illumination exit feature will activate the courtesy lamps when the key IN input of the body control module (BCM) transitions from an active state to an inactive state (removing the ignition key). When the key is removed from the ignition, the key IN input to the BCM becomes inactive. The BCM will illuminate the courtesy lamps for approximately 25 seconds, unless another BCM function causes the lamps to remain active.

Inadvertent Power Feature

Inadvertent power feature provides a similar function for the interior lamps as a retained accessory power feature. The body control module (BCM) will energize the courtesy lamps supply voltage circuit when the BCM is in the active state (awake). When the courtesy lamps supply voltage circuit is energized, it supplies voltage to all the interior lights. The BCM will continue to supply voltage to the interior lamps after the ignition is turned OFF so that the interior lamps may be operated.

The inadvertent power feature will also act as battery run down protection by deactivate the courtesy lamps supply voltage circuit after 20 minutes once the BCM becomes inactive (ignition OFF and no BCM input activity.)

Theater Dimming

The theater dimming feature will slowly dim the dimmer from full brightness to OFF. The following actions will over ride the theater dimming feature causing the courtesy lamps to deactivate immediately if no other body control module (BCM) function commands the courtesy lamps on:

    • A transition from active to inactive of the dimmer switch, turning off the dimmer switch
    • A LOCK command from the remote keyless entry system
    • A last door closed locking function (locking and closing all the doors)

Courtesy Lamps Manual Operation

The courtesy lamps may be manually operated by the dimmer switch. When the dimmer switch is placed in the ON position the body control module (BCM) receives a ground from the courtesy lamp switch signal circuit. Upon receiving this signal the BCM then pulls low the interior lamp control circuit, which illuminates the courtesy lamps. The voltage for all interior lamps is supplied by the courtesy lamp supply voltage circuit of the BCM, whenever the BCM is active. The dimmer switch will override any BCM operation of the interior lamps, such as entry illumination.

IP Compartment Lamp

When the IP compartment is opened the IP compartment lamp illuminates, if the courtesy lamps supply voltage circuit of the body control module (BCM) is activated (BCM awake).

The IP compartment lamp illuminates when the courtesy lamps supply circuit of the BCM supplies voltage to the IP compartment lamp and the IP compartment switch closes, providing a ground path.

Foot Well Courtesy Lamp

The foot well courtesy lamps are turned ON by the dimmer switch or during illuminated entry.

During illuminated entry or when the dimmer switch is ON, the body control module (BCM) wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps. The BCM pulls the interior lamp control circuit low, providing ground to the foot well courtesy lamps and all courtesy lamps.

Inside Rear View Mirror Lamp

The inside rear view mirror lamp is turned ON by the dimmer switch, the inside rear view mirror switch, or during illuminated entry.

During illuminated entry or when the dimmer switch is ON the body control module (BCM) wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps. The BCM pulls the interior lamp control circuit low, providing ground to the inside rear view mirror lamp and all courtesy lamps.

The inside rear view mirror lamp can be turned on from the inside rear view mirror switch. The BCM supplies voltage through the courtesy lamps supply voltage circuit when the BCM is awake. Manually turning on the inside rear view mirror switch provides a ground path.

Courtesy Lamp Rear Compartment

When the rear compartment is opened, the courtesy lamp rear compartment illuminates.

When the rear compartment is opened, the rear compartment courtesy lamp switch sends a ground signal to the body control module (BCM) , waking the BCM. When the BCM wakes up it will then energize the courtesy lamps supply voltage circuit , suppling voltage to the rear compartment courtesy lamp. The rear compartment courtesy lamp switch will provide a ground path for the rear compartment courtesy lamp in order to illuminate the lamp.

Roof Rail Courtesy Lamps

The roof rail courtesy lamps are turned ON by the dimmer switch, the individual roof rail courtesy lamp switch, or during illuminated entry.

During illuminated entry or when the dimmer switch is ON the body control module (BCM) wakes up and then energizes the courtesy lamps supply voltage circuit, suppling voltage to all interior lamps. The BCM pulls the interior lamp control circuit low, providing ground to the roof rail courtesy lamps and all courtesy lamps.

The roof rail courtesy lamps can be turned on from the individual roof rail courtesy lamp switch. The BCM supplies voltage through the courtesy lamps supply voltage circuit when the BCM is awake. Manually turning on the roof rail courtesy lamp switch provides a ground path.

Vanity Mirror Lamps

When the vanity mirror cover is opened, the vanity mirror lamp illuminates.

The vanity mirror lamps receive voltage from the courtesy lamps supply voltage circuit anytime the body control module (BCM) is awake. The vanity mirror lamps receive ground from their individual switches when the vanity mirror is open.

Interior Lamps Dimming

The second group of lamps include lamps which may be dimmed. This group may use a combination of vacuum fluorescent (VF) illumination and of incandescent lamps.

    • Automatic transaxle control position indicator bulb
    • Ignition control switch
    • Fog lamp switch
    • Hazard switch
    • Door switches and window switches
    • HVAC control head assembly
    • Outside remote control rear view mirror
    • Radio
    • Radio control switches
    • Trip odometer reset switch
    • Rear compartment rod release switch
    • The instrument panel cluster (IPC)
    • Heated seat switches
    • Electronic traction control switch

When the headlamp switch placed in the PARK LPS battery voltage is supplied through the headlamp switch to the TAIL LAMP, LIC LAMPS fuse.

Battery voltage is then applied thorough the tail lamp fused circuit to the panel dimming fuse. Battery positive voltage is applied from the panel dimming fuse to the IP lamp dimmer switch. The dimmer switch varies the voltage level to the interior dimming lamps, and dims or brightens the dimming lamps accordingly.

Driver Controls and Modules

    • The body control module (BCM)
    • The instrument panel cluster (IPC)

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

Driver controls include the following components.

    • The dimmer switch
    • The door jamb switches
    • The headlamp switch
    • The rear compartment lid ajar switch
    • The IP compartment lamp and switch
    • The fog lamp switch

Battery Rundown Protection / Inadvertent Power

The body control module used in this vehicle controls the lighting system through circuits that enable both the exterior lamp functions of park, head and 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 will reset for another 20 minutes.