Outside Air Temperature Display

The Ambient Air Temperature (AAT) sensor is hardwired to the Powertrain Control Module (PCM) through separate input and return circuits. The Powertrain Control Module (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 Powertrain Control Module (PCM) messages the outside air temperature data to the Heating, Ventilation, and Air Conditioning (HVAC) module through the Body Control Module (BCM). The Heating, Ventilation, and Air Conditioning (HVAC) filters the temperature data and sends the updated temperature status back to the Body Control Module (BCM). The Body Control Module (BCM) in turn messages the outside air temperature in degrees Celsius (metric) to the Instrument Panel Cluster (IPC). When the Fahrenheit (English) display is selected by the driver, the Instrument Panel Cluster (IPC) converts the Celsius to Fahrenheit and displays the temperature in the message center.

The Heating, Ventilation, and Air Conditioning (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 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.