GMC Yukon Denali 2003 Owner's Manual page 351

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 from the vehicle.
4. Press the locking release lever, turn the bulb socket
counterclockwise and remove it from the turn signal
housing.
5. Remove the bulb from the bulb socket.
6. Put the new bulb into the bulb socket.
7. Put the bulb socket into the turn signal housing and
turn it clockwise until it locks.
8. Put the turn signal housing back onto the vehicle
placing the hook and posts on the inner side into
the alignment holes first and 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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