GMC 2001 Sierra 1500 Pickup Owner's Manual page 388

Center High-Mounted Stoplamp (CHMSL)
and Cargo Lamp
1. Remove the screws and lift off the lamp assembly.
6-46
A. Cargo Lamps
-
B. Center High Mounted Stoplamps
2. Remove the CHMSL bulb holder back plate from
the housing by pressing the release tabs.
3. A CHMSL bulb is removed by pulling the bulb
straight out from the holder back plate. A cargo bulb
is removed by turning the socket counterclockwise
and pulling the bulb straight out.