2010 Cadillac CTS Owner's Manual - Page 237

Climate Controls Sensors 7-5 Do not cover the sensors or the automatic climate control system will not work properly. Air Quality Sensor For vehicles with an air quality sensor, the climate control system adjusts to limit some exhaust fumes from being pulled inside your vehicle. The interior temperature sensor located on the instrument panel to the right of the steering wheel, measures the temperature of the air inside the vehicle. The climate control system uses the information from these sensors to adjust the fan speed and the air delivery, in order to maintain the selected temperature. The system may also supply cooler air to the side of the vehicle facing the sun. The recirculation mode will also be activated, as necessary. Press the AUTO button on the climate control to activate the air quality sensor. The recirculation indicator light comes on when poor quality air is detected. The air quality sensor will not maintain recirculation for an extended period to prevent the air inside the vehicle from becoming too dry or stuffy. The solar sensor located on the instrument panel, near the windshield, monitors the solar heat.