GMC 2014 Yukon/Yukon XL Owner's Manual page 14

If available, raise or lower the
entire seat by moving the entire
control up or down.
See Power Seat Adjustment on
page 3-3.
If equipped, increase or decrease
manual lumbar support by turning
the knob forward or rearward.
See Lumbar Adjustment on
page 3-4.
To adjust the power lumbar support,
if equipped:
On vehicles with two-way
lumbar, press and hold the top
or bottom of the control to
increase or decrease lumbar
support.
On vehicles with four-way
lumbar, press and hold the front
or rear of the control to increase
or decrease lumbar support. To
raise or lower the height of the
support, press and hold the top
or bottom of the control.
See Lumbar Adjustment on
page 3-4.
To recline a manual seatback:
1. Lift the lever.