GM Service Manual Online
For 1990-2009 cars only

The knob for this feature is located next to the exterior lamps control.

(Instrument Panel Lights): Push the knob to extend and then turn clockwise or counterclockwise to brighten or dim the instrument panel lights and the radio display. This only works if the headlamps or parking lamps are on.

To turn on the dome lamps, with the vehicle doors closed, turn the knob all the way clockwise.