Ambient Air Temperature (AAT) Sensor
The Ambient Air Temperature (AAT) sensor is an input to the PCM. If the outside air temperature is below approximately 1°C (33.8°F), the PCM does not allow the A/C compressor clutch to engage.
After replacing an Ambient Air Temperature (AAT) sensor, the sensor data must be reset by driving the vehicle at speeds consistently above 20 MPH for at least 5 minutes to update the filtered data.