GMC 2008 Yukon Denali Owner's Manual page 24

3. Lift the lever again to release the rear of the seat
from the floor. The seat will tumble forward.
1-20
2. Lift the lever, located
on the bottom rear of
the second row seat on
the inboard side, to
release the seatback.
The seatback will
fold forward.
Automatic Release Fold and Tumble
Feature
The transmission must be in PARK (P) for this feature
to work.
Folding and Tumbling the Seat(s)
CAUTION:
{
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.
To fold and tumble the seat, do the following:
1. Make sure that there is nothing under, in front of, or
on the seat.
Notice: Folding a rear seat with the safety belts
still fastened may cause damage to the seat or the
safety belts. Always unbuckle the safety belts
and return them to their normal stowed position
before folding a rear seat.