Manual Operation of Power Liftgate
To change the liftgate to manual operation, turn the mode switch to the OFF position.
With the power liftgate disabled and all of the doors unlocked, the liftgate can be manually opened and closed. Manual operation of a liftgate that also has power operation requires more effort than a standard manual liftgate.
To open the liftgate, press the touch pad on the handle on the outside of the liftgate, and lift the gate open. To close the liftgate, use the pull cup to lower the liftgate and close. With the power liftgate disabled, the liftgate electric latch will still power latch once contact is made with the striker. Always close the liftgate before driving.
If 
on the RKE transmitter is pressed
while power operation is disabled, the turn signals flash and the liftgate will
not move.
The liftgate has an electric latch. If the battery is disconnected or has low voltage, the liftgate will not open. The liftgate will resume operation when the battery is reconnected and charged.
See also:
Customer Assistance Offices (U.S. and Canada)
GMC encourages customers to call the toll-free number for assistance.
However, if a customer wishes to write or e-mail GMC, the letter should be addressed to:
United States
GMC Customer Assistance ...
Using this Manual
To quickly locate information about the vehicle, use the Index in the back of the manual. It is an alphabetical list of what is in the manual and the page number where it can be found. ...
Cargo Cover
For vehicles with a cargo cover, use it to cover items in the rear of the vehicle.
To remove the cover from the vehicle, pull both ends toward each other. To reinstall,
place each end of the cover ...