GMC Yukon 2007 Owner's Manual page 134

Your vehicle has pinch sensors located on the
side edges of the liftgate. If an object is caught
between the liftgate and the body and presses
against this sensor, the liftgate will reverse
direction and open fully. The liftgate will remain
open until it is activated again or closed manually.
Manual Operation of Power Liftgate
With the power liftgate disabled and the door
unlocked, the power liftgate can be manually
opened and closed.
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To change the liftgate to
manual operation,
toggle the switch on the
overhead console to
the "Disable" position
indicated by a circle.
To open the liftgate, press the touchpad on the
handle on the outside of the liftgate, and lift
the gate open. To close the liftgate, use the pull
cup or pull strap to lower the liftgate and close.
The liftgate latch will power cinch to closed
position. Always close the liftgate before driving.
If the RKE button or the power close button on the
liftgate is pressed while power operation is
disabled, the lights will flash three times, but the
liftgate will not move.
It is not recommended that you drive with the
liftgate open, however, if you must drive with the
liftgate open, the power liftgate should be switched
to manual liftgate operation — the overhead
console switch set to the "Disable" position.
Both the liftglass and liftgate have an electric latch.
If the battery is disconnected or has low voltage,
the liftglass and liftgate will not open. The
liftglass and liftgate will resume operation when
the battery is reconnected and charged.
If the battery is properly connected and has
adequate voltage, and the liftgate or liftglass still
will not function, your vehicle should be taken to a
dealership for service.