GMC 2002 Yukon Denali Owner's Manual page 145

Global positioning capabilities will not be available if
satellite signals are obstructed.
OnStar will not function if the vehicle's battery is
discharged or disconnected. It may also be inoperative if
the vehicle is in an accident and the OnStar or vehicle
electrical system components are damaged.
OnStar is the communication link between you and
existing governmental emergency roadside service
providers. OnStar will receive your call and use
reasonable effort to contact an appropriate provider.
OnStar cannot promise that the providers will respond in
a timely manner or at all.
Sunroof (If Equipped)
Your vehicle may be equipped with a power sliding
sunroof. To open or close your sunroof, the ignition
needs to be on or RAP needs to be active. See "Retained
Accessory Power" in the Index.
Press and release the rear side of the button located in
the front overhead console to express
panel and sunshade. To close the glass panel, press and
hold the front of the button. The glass will not be fully
seated unless the button is held until the glass stops
moving. With the sunroof closed, press the forward side
of the button to open the sunroof to the vent position.
-
open the glass
2-57