Theory Of Operation
The Ambient Air Temperature Sensor is a two wire sensor that is hard wired to the Drivers Door Module (DDM). On some vehicles not equipped with DDM, the wiring goes directly to the Body Control Module (BCM). The DDM (or BCM) supplies a 5-Volt signal and a sensor ground to the Ambient Air Temperature (AAT) Sensor. The sensor internal resistance changes in response to changes in ambient temperature. In both options, it is the BCM that broadcasts the AAT Sensor signal over the Can C Bus. The Powertrain Control Module (PCM) acquires the AAT Sensor signal from the Can C Bus.
If a repair is performed to the AAT Sensor wiring, or a sensor is replaced to correct and active DTC, the vehicle must be driven for a minimum of 5 minutes above 15 mph to update the AAT temp signal before the DTC will go stored and can be erased.