GM Service Manual Online
For 1990-2009 cars only

Interior Lamps

The interior lighting consists of the dome lamp.

Dome Lamps

The dome lamp, may be manually turned ON or OFF by placing the interior lamp switch in the ON, DOOR or OFF position. When the driver places the dome lamp switch in the ON position, the dome lamps will remain on. When the driver places the dome lamp switch in the DOOR position, and a door is opened, the dome lamp will illuminate. When the driver places the dome lamp switch in the OFF position, the dome lamp will be disabled.

A circuit breaker in the instrument panel (I/P) supplies battery positive voltage to the dome lamp switch. A normally open door jamb switch provides a ground circuit when a door is opened. A diode module is used to prevent a voltage feed back from the turn/hazard switch. If the dome lamp switch is placed in the ON position, the dome lamp will remain ON until turned OFF or the battery runs dead.

Interior Lamps Dimming

The second group includes lamps which may be dimmed.

    • HVAC control head assembly
    • Radio
    • The instrument panel cluster (IPC)
    • Various transmission control switches

A circuit breaker in the I/P supplies battery positive voltage to both the tail lamp relay coil circuit and switch circuit. When the driver places the headlamp switch in either the PARK or HEADLAMP position, the tail lamp relay is energized. The tail lamp relay coil circuit is grounded through the headlamp switch at G105. When the tail lamp relay is energized battery positive voltage is supplied to all lamps in the dimming circuit. When the driver selects a dimming setting by moving, the I/P dimming switch potentiometer, all incandescent back lighting lamps are provided with a specific voltage. The incandescent back lighting lamps are then grounded at G105.

Driver Controls & Modules

Driver controls include the following components.

    • The emergency flasher switch
    • The headlamp dimmer switch
    • The headlamp switch
    • The dome lamp switch
    • The I/P dimmer switch
    • The stop lamp switch
    • The turn signal switch

Two modules process the inputs and the controls.

    • The transmission control module (TCM)
    • The vehicle interface module (VIM)