Chevrolet 2011 Express 1500 Cargo Owner's Manual page 312

The Center High-Mounted Stoplamp
(CHMSL) is located above the rear
doors at the center of the vehicle.
To replace a bulb:
1. Remove the two screws from the
CHMSL assembly.
2. Remove the CHMSL assembly.
3. Turn the bulb socket
counterclockwise one quarter
turn to remove it from the lamp
assembly.
4. Pull the old bulb straight out of
the socket and push the new
bulb into the socket.
5. Turn the bulb socket clockwise
one quarter turn to install it in the
lamp assembly.
6. Reinstall the CHMSL assembly
and two screws.
Do not block or damage the CHMSL
when items are loaded on the roof
of the vehicle.
To replace one of these bulbs:
A. Bulb Socket
B. License Plate Bulb Assembly
C. Screws