GMC 1996 Sierra Owner's Manual page 293

Sidemarker Lamps
I . Remove the screws and
pull out the parkingkurn
signal lamp assembly.
2. Reach through the opening and turn the sidemarker
bulb socket counterclockwise and remove it.
3. Pull the bulb straight out
of the socket.
4. Put a new bulb into the socket and push it in until
it
is tight.
5 . Put the socket back into the sidemarker assembly
and turn
it
clockwise
t o
tighten it.
6. Replace the parking/turn signal lamp assembly and
tighten the screws.