GM Service Manual Online
For 1990-2009 cars only

Interior Lamps

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

Dome Lamp

The CTSY LAMPS circuit breaker in the instrument panel (IP) fuse block supplies battery positive voltage to the dome lamp. A path to ground is provided for the dome lamp through the IP lamps dimmer switch or the door jamb switch. When the driver places the IP dimmer switch in the dome lamp ON position or opens the driver door, the dome lamp will illuminate.

When the driver uses the keyless entry transmitter to unlock the doors, the remote keyless door lock receiver (RCDLR) will keep the dome lamp on approximately 40 seconds. When the driver uses the transmitter to lock the doors, the RCDLR will keep the dome lamp on approximately 2 seconds. When the ignition switch is turned to either the RUN or CRANK position, the dome lamp will turn OFF immediately.

Reading Lamps

Similar to dome lamp, reading lamps receive battery voltage through a CTSY LAMPS fuse in the I/P fuse block. When the reading lamp switch is turned ON, the switch contacts close, supplying ground to the reading lamp, that in turn illuminates.

Interior Lamps Dimming

This group includes lamps which may be dimmed. The dimmer switch is powered by two fuses: GAGES and PARK LAMP fuse. As the user operates the dimmer switch potentiometer, the output voltage to ILLUM fuse varies. Varied voltage passes through ILLUM fuse to the following components:

    • Instrument panel cluster (IPC)
    • Inflatable restraint I/P module disable switch, RPO AK5 w/o AQR
    • Automatic transmission fluid temperature (TFT) gage, RPO UXT
    • Air brake pressure gage lamp, JE4
    • HVAC control assembly
    • Automatic transmission shift selector, LG4/LG5
    • Auxiliary HVAC control assembly, C36