2004 GMC Sierra 1500 Pickup Owner's Manual - Page 182

Auxiliary Roof Mounted Lamp Switch If your vehicle has this feature, this switch includes wiring provisions for a dealer or a qualified service center to install an auxiliary roof lamp. This switch is located on the center of the instrument panel near the comfort controls. Cargo Lamp The cargo lamp button is located on the left side of the instrument panel. Press the button to turn the cargo lamp on. Press the button again to turn it off. An indicator light on the instrument panel will illuminate when the cargo lamp is turned on and the ignition key is turned to RUN. When the switch wiring is connected to an auxiliary roof mounted lamp, pressing the switch will activate the lamp and illuminate an indicator light near the switch. Pressing the switch again will turn off the roof mounted lamp. If your vehicle has this switch, your vehicle may have the snow plow prep package. For further information see "Snow Plow Prep Package″. 3-18