GM Service Manual Online
For 1990-2009 cars only

Interior Lamps

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

    • Cargo lamp
    • Console courtesy lamps
    • Courtesy/Illuminated entry lamps
    • Dome lamps
    • Door courtesy lamps
    • I/P courtesy lamps
    • I/P compartment lamp
    • Map lamps
    • Reading lamps
    • Vanity mirror lamps

Courtesy/Illuminated Entry Lamps

The courtesy/illuminated lamps, may be manually turned on or off by placing the interior lamp switch in the ON or OFF position. When the driver places the dome lamp defeat switch in the OFF position, the courtesy/illuminated entry lamps will be disabled. If an outside door handle is lifted or a door is opened, the courtesy/illuminated entry lamps illuminate. After all the doors have been closed the courtesy/illuminated entry lamps will remain illuminated approximately 15 seconds. The courtesy/illuminated entry lamps will also turn on prior to any door being opened, and remain illuminated approximately 40 seconds when the driver removes the ignition key.

The courtesy/illuminated entry lamps, include two different groups of lamps. The first group includes these courtesy/illuminated entry lamps which are not individually controlled:

    • Dome lamps
    • Door courtesy lamps
    • I/P courtesy lamps

These lamps illuminate when a door jamb switch, courtesy lamp switch or a remote keyless entry (RKE) command is received by the body control module (BCM).

The CTSY LP 15A fuse in the engine wiring harness junction block, supplies battery positive voltage to the inadvertent power relay coil and switch circuits. The BCM provides a ground to control the inadvertent power relay. The normally open Inadvertent power relay switch closes and provides power to these courtesy lamps. When a courtesy lamp request input is received by the BCM, the BCM will energize the courtesy lamp relay. The normally open courtesy lamp relay switch closes, illuminating the lamps by grounding the courtesy lamp ground circuit to G203.

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 second group includes these individually controlled lamps, each with a separate switch:

    • I/P compartment lamp
    • Map lamps
    • Reading lamps
    • Underhood lamp
    • Vanity mirror lamps

The CTSY LP 15A fuse in the engine wiring harness junction block, supplies battery positive voltage to the inadvertent power relay coil and switch circuits. The BCM provides ground to energize the inadvertent power relay, which provides voltage to these lamps. Ground is provided to the I/P compartment lamp at G200. Ground is provided to the underhood lamp at G102. Ground is provided to all others at G203.

Courtesy/Illuminated Entry Lamps (Luxury-Y91)

The courtesy/illuminated entry lamps, may be manually turned on or off by placing the interior lamp switch in the ON or OFF position. When the driver places the dome lamp defeat switch in the ON position, the courtesy/illuminated entry lamps will be disabled. If an outside door handle is lifted or a door is opened, the courtesy/illuminated entry lamps illuminate. After all the doors have been closed the courtesy/illuminated entry lamps will remain illuminated approximately 15 seconds. The courtesy/illuminated entry lamps will also turn on prior to any door being opened, and remain illuminated approximately 40 seconds when the driver removes the ignition key.

The courtesy/illuminated entry lamps, include two different groups of lamps. The first group includes these courtesy/illuminated entry lamps which are not individually controlled:

    • Console courtesy lamps
    • Dome lamps
    • Door courtesy lamps
    • I/P courtesy lamps

These lamps illuminate when a door jamb switch, courtesy lamp switch or a remote keyless entry (RKE) command is received by the body control module (BCM).

The CTSY LP 15A fuse in the engine wiring harness junction block, supplies battery positive voltage to the inadvertent power relay coil and switch circuits. When a courtesy lamp request input is received by the body control module (BCM), the BCM provides ground to the inadvertent power relay to signal the courtesy lamp module. The courtesy lamp module provides pulse width modulation (PWM) voltage to the courtesy lamps. Ground is provided at all times at G203.

The courtesy lamps will normally turn off using the theater dimming feature controlled by BCM with PWM. 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 second group includes these individually controlled lamps, each with a separate switch:

    • I/P compartment lamp
    • Map lamps
    • Reading lamps
    • Underhood lamp
    • Vanity mirror lamps

The CTSY LP 15A fuse in the engine wiring harness junction block, supplies battery positive voltage to the inadvertent power relay coil and switch circuits. The body control module (BCM) provides ground to energize the inadvertent power relay and power these lamps. Ground is provided to the I/P compartment lamp at G200. Ground is provided to the Underhood lamp at G102. All others are grounded at G203.

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 40 seconds. When the driver uses the remote function actuator transmitter to lock the doors, the BCM will keep the courtesy lamps on approximately 2 seconds. 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 inadvertent power relay 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. The vanity lamps are grounded at G203.

IP Compartment Lamp

The inadvertent power relay 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. The IP compartment lamp is grounded at G102.

Cargo Lamp

The inadvertent power relay 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.

Battery Rundown Protection/Inadvertent Power

In the event that any of the interior lamps supplied voltage by the inadvertent power relay and ground from the courtesy lamp relay were to remain on when the ignition is OFF after a period of 20 minutes, the BCM will deactivate the inadvertent power relay turning OFF all of the lamps on that circuit to prevent total battery discharge. Only when the ignition switch is cycled back to the RUN position will the BCM reset the internal timer and reactivate the inadvertent power relay. When the inadvertent power relay is not energized, the BCM utilizes the inadvertent power courtesy lamp supply voltage circuit to monitor for a courtesy lamp switch request signal. If a courtesy lamp switch is activated, the BCM will receive the signal to energize the inadvertent power relay by grounding the control circuit.

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.

    • Door switches and window switches
    • HVAC control head assembly
    • Radio
    • The instrument panel cluster (IPC)
    • Other interior controls and switches

When the ignition switch is turned to the ON position, the radio's vacuum fluorescent (VF) displays turn on at maximum brightness. When the park lamps are on, 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. Battery positive voltage is supplied through the PARK LPS 30 A fuse in the engine wiring harness junction block, to the normally open park lamp relay switch contacts. The panel dimmer switch potentiometer receives both its voltage and ground from the headlamp switch and is an input to the BCM. 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 G203 and G200. 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.