GMC Sierra 2014 Owner's Manual page 59

The sunroof also has a sunshade,
which can be pulled forward to block
sun rays. The sunshade must be
opened and closed manually.
If an object is in the path of the
sunroof while it is closing, the
anti-pinch feature will detect the
object and stop the sunroof.
Dirt and debris may collect on the
sunroof seal or in the track. This
could cause an issue with sunroof
operation or noise. It could also
plug the water drainage system.
Keys, Doors, and Windows
Periodically open the sunroof and
remove any obstacles or loose
debris. Wipe the sunroof seal and
roof sealing area using a clean
cloth, mild soap, and water. Do not
remove grease from the sunroof
tracks.
If water is seen dripping into the
water drainage system, this is
normal.
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