Outside Air Temperature Display

The Ambient Air Temperature (AAT) sensor is hardwired to the PCM through separate input and return circuits. The PCM provides a reference voltage to the Ambient Air Temperature (AAT) sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. The PCM filters the ambient air temperature input and sends the data to the GWM through the HS-CAN1. The GWM sends the air ambient temperature filtered message to the HVAC control module over the MS-CAN. The HVAC control module returns the message as the Outside Air Temperature message to the GWM. The GWM sends outside air temperature message to the APIM for the touchscreen to display the outside air temperature.

The PCM 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 Ambient Air Temperature (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 Ambient Air Temperature (AAT) sensor.

After replacing an Ambient Air Temperature (AAT) sensor, the sensor data must be reset by either driving the vehicle at speeds consistently about 20 MPH for at least 5 minutes to update the filtered data or perform the multiple button press reset procedure to update to the current raw value.

The multiple button reset for the Ambient Air Temperature (AAT) sensor is as follows:

• On the HVAC panel controls, press the A/C and Recirc buttons simultaneously, then, release both.
• Within 2 seconds press the A/C button again.