Theory Of Operation
WARNING: This page is about a different car, the 2016 Dodge Durango. However, it is still accessible from the selected car via links, so may be relevant.
The Ambient Air Temperature (AAT) Sensor rationality diagnostic runs under cold start conditions, following a start to run delay time. The diagnostic monitor compares the outputs of the ambient, engine coolant and intake air temperature sensors. If the Engine Coolant and Intake Air Temperature Sensors agree and the Ambient Air Temperature Sensor does not agree, the Ambient Air Temperature Sensor is declared as irrational. If declared irrational a second comparison will be done after a short drive cycle.