GMC 2009 Sierra - Manual (Page 366)

9. Reinstall the turn signal assembly 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.
10. Reinstall the headlamp assembly.
Center High-Mounted Stoplamp
(CHMSL) and Cargo Lamp
To replace one of these bulbs:
1. Remove the screws and lift off the lamp assembly.
A. Cargo Lamp
B. Center High-Mounted Stoplamp Bulb (CHMSL)
2. Remove the CHMSL and Cargo bulbs by turning
socket counterclockwise and pulling the bulb
straight out.
3. Install the CHMSL and Cargo bulbs by pushing the
bulb straight in and turning clockwise.
4. Reinstall the lamp assembly and tighten the screws.
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