GMC 2010 Yukon XL Denali Owner's Manual page 45

2. Lift the lever(s), located on the bottom rear of the
second row seat(s) on the inboard side, to release
the seatback. The seatback will fold forward.
3. Lift the same lever again to release the rear of the
seat from the floor. The seat will tumble forward
automatically.
Automatic Seat Release Fold and
Tumble Feature
The transmission must be in (P) for this feature
to work.
WARNING:
Automatically folding and tumbling the seat when
someone is sitting in the seat, could cause injury
to the person sitting there. Always make sure
there is no one sitting in the seat before pressing
the automatic seat release button.
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