Outside Air Temperature Display

The AAT sensor is hardwired to the PCM through separate input and return circuits. The PCM provides a reference voltage to the AAT sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. The PCM messages the outside air temperature data to the HVAC module through the BCM. The HVAC filters the temperature data and sends the updated temperature status back to the BCM. The BCM in turn messages the outside air temperature in degrees Celsius (metric) to the IPC. When the Fahrenheit (English) display is selected by the driver, the IPC converts the Celsius to Fahrenheit and displays the temperature in the message center.

The HVAC module is programmed to update the messaged outside temperature data at different rates depending on several criteria to prevent false temperature displays due to a condition known as heat soaking. Heat soaking is where the outside air temperature is hotter in the location of the AAT sensor than the actual outside air temperature.

When the sensed outside temperature rises, the display updates slowly at varying rates based on vehicle speed. When the sensed outside temperature drops, the display updates more quickly following the drop experienced by the AAT sensor.