Ambient Air Temperature Sensor

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The ambient air temperature sensor is a 2-wire negative temperature co-efficient thermistor.

A 5-volt reference and signal circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases.

The sensor operates within a temperature range of -40°C to +60°C (-40°F to +140°F). The HVAC control module receives a class 2 message from the instrument panel cluster (IPC). The ambient air temperature sensor is mounted in the forward engine area, behind the left front headlamp. This causes an air flow issue due to the sensor's location and can effect the ambient air update display parameter in the DIC of the vehicle. For model year 2008 the ambient air temperature sensor will have a new location closer to the grill airflow. In the present position, it is exposed to limited airflow from the grill before it reaches the radiator. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a working temperature range.

The ambient air temperature sensor algorithm uses 3 pieces of information, outside air temperature data, vehicle speed, and time the engine was turned off.

The ambient air temperature is updated and displayed by the DIC under the following conditions:

Conditions	DIC Display
If the current ambient air temperature value is cooler than or equal to the old temperature value. Vehicle speed is in excess of 33 mph.	Displays outside actual temperature. Display updates every second.
If the current ambient air temperature value is warmer than the old temperature value. Vehicle speed is less than or drops below 18 mph.	Displays last temperature recorded during last ignition cycle. No update.
New ambient temperature exceeds the previous ignition cycle recorded ambient temperature, and vehicle speed exceeds 18 mph but is less than 33 mph.	Displays outside actual temperature. Display will be updated at a slow rate.
Vehicle speed is greater than or equal to 45 mph. (for at least 3 minutes)	Displays outside actual temperature Display updates at a quicker rate.