GMC Denali 2004 Owner's Manual page 343

2. Press the retainer clip (B), located behind the turn
signal housing, towards the outside of the vehicle.
3. Pull the turn signal housing out of the vehicle.
4. Press the locking release lever, turn the bulb socket
counterclockwise and remove it from the turn signal
housing.
5. Remove the old bulb from the bulb socket.
6. Put a new bulb into the bulb socket. Use care not
to touch the bulb with your fingers or hands.
7. Put the bulb socket back into the turn signal
housing and turn it clockwise until it locks.
8. Put the turn signal housing back into the vehicle
placing the hook and posts on the inner side into
the alignment holes first, then the outer side into the
retainer bracket until you hear a click.
9. Put the headlamp assembly back into the vehicle.
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