GMC 2009 Yukon XL Owner's Manual page 216

Mimic Mode: This mode matches the rear climate
control to the front climate control airflow settings.
It comes on when REAR is pressed the first time.
Independent Mode: This mode directs rear seating
airflow according to the settings of the rear controls.
It comes on when any rear control is adjusted.
Temperature Control: Turn clockwise or
counterclockwise to increase or decrease the
airflow temperature into the passenger area.
Fan Control: Turn clockwise or counterclockwise to
increase or decrease the fan speed.
Air Delivery Mode Control: Turn clockwise or
counterclockwise to change the direction of the airflow.
3-32
H
(Vent): Air is directed through the headliner outlets.
)
(Bi-Level): Air is directed through the floor and
headliner outlets. The rear system floor outlets
are located directly behind the second row seats.
The flow can be divided between vent and floor outlets
depending upon where the knob is placed between
the settings.
6
(Floor): Air is directed to the floor outlets. The rear
system floor outlets are located directly behind the
second row seats.