2008 GMC Envoy Owner's Manual - Page 163

P (On/Off): Press this button to turn the rear climate controls on or off. z9 y (Fan): Press this button to adjust the fan speed. z\ y (Mode): Press this button to change the direction of airflow (panel, bi-level or floor) to the rear seat area. The rear control only turns on if the front climate control system is on and not in defrost mode. If your vehicle has the rear seat audio system, the lower buttons are used to adjust the rear seat climate control system. The temperature of the air coming through the rear outlets is determined by the front passenger temperature setting. 3-29