GMC 2004 Sierra - Manual (Page 473)

4. Pull the old bulb straight out from the socket.
5. Press a new bulb into the socket and turn the socket
clockwise into the taillamp housing.
6. Reinstall the rear lamp assembly.
7. Close the tailgate.
Taillamps (Chassis Cab Models)
A. Turn Signal Lamp
B. Stoplamp
C. Back-up Lamp
1. Using your hands, peel the rubber seal away from
the lens.
2. Lift the lens off the lamp assembly.
3. Pull the old bulb straight out from the socket.
4. Put a new bulb into the socket and press it in until it
is tight.
5. Reinstall the lens and the lens seal.
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