Ambient Air Temperature Sensor

WARNING: This page is about a different car, the 2018 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

The Ambient Air Temperature (AAT) sensor is a Negative Temperature Coefficient (NTC) type sensor. The AAT sensor allows the Powertrain Control Module (PCM) to monitor the temperature of the air around the vehicle.

The PCM uses the AAT sensor input along with other in-car temperature sensors to control:

Vehicles interior temperature
Engine coolant temperature using the electric cooling fan.
The AAT sensor is installed in the left door mirror, with the bulb of the sensor positioned over a hole in the bottom of the door mirror cover.

The PCM supplies the sensor with a 5 V reference voltage and a ground, and translates the return signal voltage into a temperature value.

If there is a fault with the AAT sensor, the PCM calculates the ambient air temperature. The PCM uses for the calculation the temperature input of the Mass Air Flow and Temperature (MAFT) sensor. If the AAT sensor and the temperature inputs of the MAFT sensor are all faulty, the PCM adopts a default ambient temperature of 25°C (77°F).