Ambient Temperature Sensor / Switch HVAC: Description and Operation

This sensor is located in a small protective housing just to the rear of the radiator grille. The sensor data is processed by the Body Control Module (BCM) and displayed on the Climate Control Driver Information Center (CCDIC).


During periods of city traffic and idle conditions, engine heat can surround the area of the outside temperature sensor and cause temperature readings that are higher than the actual outside air temperature. To help eliminate these "false" readings, programming techniques are used to minimize unwanted temperature variations.

A temperature "memory" feature is used in the BCM outside temperature programming to help provide greater accuracy under engine restart conditions. If engine coolant temperature is less than 10°C (50°F) above the outside temperature sensor reading, the actual sensed outside temperature is displayed. However, if engine coolant is greater than 10°C (50°F) above the sensor reading, "memorized 1" outside temperature is displayed. This is the temperature sensed when the engine was previously operating.

Also, at car speeds less than or equal to 20 mph, the BCM limits the displayed temperature value to an increase rate of one degree every 100 seconds. This compensates for the artificially hot area around the sensor caused by city traffic and idle conditions. At car speeds between 20 and 45 mph, the outside temperature display is allowed to increase but only after a built-in two minute time delay allows for outside air to cool around the sensor. The two minute time delay starts when vehicle speed reaches 20 mph. At car speeds above 45 mph or if the sensor reading is ever less then the displayed value, there is no delay and outside temperature changes are displayed as rapidly as possible.