2008 GMC Yukon Owner's Manual - Page 209

Rear Air Conditioning and Heating System and Electronic Climate Controls For vehicles with the rear heat and air conditioning controls, they are integrated with the rear seat audio controls located in the center console. The system can be controlled from the front controls as well as the rear controls. To turn the system on, press the AUX button on the front climate control system, an indicator will be lit. Pressing the AUX button the first time will turn the rear system on in a mimic mode. In this mode, the airflow in the rear will be approximately the same direction, temperature, and fan speed as the front. Pressing the AUX button again turns the rear system and the indicator off. If the rear controls are adjusted, the system enters a rear independent mode. Airflow in the rear will then be directed according to the settings of rear controls. The rear system can be turned off by pressing the AUX button on the front climate control system and the indicator will turn off. If the indicator in the front AUX button is off, the rear system is off. To turn the system on from the rear, press any rear climate control button, except the C button. To turn the system off, press and hold the C button. Rear Climate Control with Rear Seat Audio Controls 3-35