Description And Operation: Operation

The Body Control Module (BCM) is the master of the ambient air temperature. It provides raw ambient air temperature and averaged ambient air temperature. Raw ambient temperature is what the sensor reads. This information is provided to the Powertrain Control Module (PCM) at a very fast rate. Averaged ambient air temperature is a complex algorithm and it is the temperature that is provided to the customer (displayed on the Instrument Panel Cluster/IPC and radio module) at a rate of once per second or upon a temperature change. All other modules, for example heated seats, use this averaged ambient air temperature.

Auto ON Feature and Ambient Temperature 

The vehicle needs to be OFF for about 3.5 hours before it will take in raw or instantaneous readings and provide it to the customer. This is to ensure that false readings are not displayed due to engine heat soak. Readings also depend on where the vehicle is stored. If the vehicle is parked in a garage for 5 hours where it could be 10°C (50°F) and outside temperature is -1°C (30°F), then the vehicle would display 10°C (50°F). The customer would have to drive the vehicle for 20 seconds above 32 km/h (20 mph) before it would start to update (± 1° is allowed per second) and trend towards true outdoor temperature of -1°C (30°F). If the outside ambient air temperature is cold enough to warrant the auto comfort features such as heated seats and heated steering wheel but the vehicle is stored in a garage where the temperature is at an amount that does not warrant these features, they will not auto activate.

The ambient air temperature sensor is diagnosed using a scan tool. Refer to STANDARD PROCEDURE . Also. Refer to SENSOR, AMBIENT TEMPERATURE, DIAGNOSIS AND TESTING .