GM Service Manual Online
For 1990-2009 cars only

Interior Lighting

The interior lighting consists of lamps that may not be dimmed (Interior Lamps) and lamps that may be dimmed (Interior Lamps Dimming). The courtesy, reading, cargo, and vanity lamps are grounded at G302 at all times.

Interior Lamps

The first group of lamps are the interior courtesy lamps that may not be dimmed manually, these include:

    • The cargo lamp
    • The courtesy/reading lamps
    • The roof rail reading 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 (RKE) 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 20 minutes after removing the ignition key and closing all doors to prevent battery rundown.
    • A theatre dimming feature that can slowly dim the interior lamps from full brightness to OFF
    • An instrument panel (I/P) dimmer switch, for manual control of the courtesy lamps
    • Courtesy lamps defeat which allows the lamps to remain OFF when the doors are opened and for illuminated entry/exit.
    • Individual switches for control of the reading and vanity lamps

Courtesy/Illuminated Entry Lamps

The courtesy lamp high control circuit supplies voltage to the courtesy lamps and cargo lamps. The lamps are illuminated when they receive a battery positive voltage from the courtesy lamp high control circuit of the body control module (BCM). The BCM will supply voltage to the courtesy lamp high control circuit for illuminated entry under the following conditions:

    • The ignition is in the LOCK position.
    • The I/P dimmer switch is in the door position.
    • The door jamb input transitions to an active state (opening a door).
    • The use of the RKE to unlock the side doors

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 the door latch switch signal circuit is active with the ignition in the OFF position, the BCM will illuminate the courtesy lamps. The courtesy lamps will remain illuminated for approximately 25 seconds after the door latch switch signal circuit becomes inactive, 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 illuminated exit feature will activate the courtesy lamps when the KEY IN input of the 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 BCM will energize the courtesy lamp high control circuit and the inadvertent power courtesy lamp circuits when the BCM is in the active state (awake). When these circuits are energized, voltage is to all the interior lights, including the courtesy, cargo, reading, and vanity lamps. Any time a switch is activated to the ON position the BCM will wake up and apply voltage to the 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 deactivating the circuits after 20 minutes once the BCM becomes inactive (ignition OFF and no BCM input activity.)

Theater Dimming

The theatre dimming feature that can slowly dim the interior lamps from full brightness to OFF with pulse width modulation (PWM). The following actions will override the theatre dimming feature causing the courtesy lamps to deactivate immediately if no other BCM function commands the courtesy lamps ON:

    • A transition from active to inactive of the interior lamps switch (turning off the interior lamps switch)
    • A LOCK command from the RKE 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 I/P dimmer switch. When the I/P dimmer switch is placed in the ON position, the BCM receives a ground signal from the courtesy lamps ON switch signal circuit. Upon receiving the courtesy lamp switch signal, the BCM then applies battery positive voltage to the courtesy lamp high control circuit, which illuminates the courtesy lamps. The interior lamp switch will override any BCM operation of the interior lamps, such as entry illumination.

Roof Rail Reading Lamps

The roof rail reading lamps receive voltage on the inadvertent power courtesy lamp circuit, and are turned ON by the individual switch on the lamp assembly.

Courtesy/Reading Lamps

The courtesy/reading lamps receive voltage in 2 ways. The reading lamps receive voltage on the inadvertent power courtesy lamp circuit, which has voltage any time the BCM is awake, and are turned ON by the individual switch on the lamp assembly. The courtesy lamps receive voltage on the courtesy lamp high control circuit, controlled by the BCM.

Vanity Mirror Lamps

When the vanity mirror cover on the sunshade is opened, the sunshade mirror lamp illuminates. The vanity mirror lamps receive voltage on the inadvertent power courtesy lamp circuit, which has voltage any time the BCM is awake, and are turned ON by the individual switch.

Interior Lamps Dimming

The second group of lamps include lamps which may be dimmed. These lamps include:

    • The instrument panel cluster (IPC)
    • Door lock, window, seat, switches
    • HVAC control head assembly
    • Outside rearview mirror switches
    • Radio
    • Steering wheel controls
    • I/P multifunction switch
    • Overhead console multifunction switch
    • The headlamp switch
    • Garage door opener

Any time the body control module (BCM) activates the headlamps or park lamps, the interior dimming lamps are also activated. The BCM applies a voltage reference and a low reference signal to the panel dimmer switch. The BCM then receives a variable signal from the panel dimmer switch to indicate the desired lamp intensity. The BCM then applies the voltage necessary through the instrument panel lamp supply voltage to all dimming lamps.

Parade Mode

Parade mode is entered when the vehicles headlamp switch is in the "ON" position during daytime lighting conditions.

When Parade Mode is active, the cluster shall set all displays and Indicators to maximum daytime brightness, pointer shall not be illuminated.

    • This condition (Parade Mode) ONLY happens during daytime and headlamps switch is ON.
    • At night time there is no way to turn off the pointers backlighting.
    • Gages with ignition in OFF/LOCK. You can see all pointer at zero.
    • Gages with ignition in RUN. You can not see any pointers.

Modules and Driver Controls

The BCM module processes the inputs and outputs for most of the interior lamps, with the exception of the reading and vanity lamps, which receive voltage from the BCM, and control on the ground side of the lamps integral switches. Driver controls include the following components:

    • The instrument panel (I/P) dimmer switch
    • The jamb or ajar switches
    • The headlamp switch
    • The reading lamp switches
    • The vanity mirror lamps switches