Circuit/System Description

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 variable resistor interfaced to the body control module (BCM). The BCM monitors the ambient air temperature sensor. The ambient air temperature sensor is a 2-wire negative temperature coefficient thermistor. The BCM applies 5 volts to an internal input resistor connected to the signal circuit of the ambient air temperature sensor. The BCM also provides the ground to the ambient air temperature sensor through the low reference circuit. When the ambient air temperature is cold, the sensor resistance is high and the signal voltage is high. When the ambient air temperature is hot, the sensor resistance is low and the voltage signal is low. The BCM provides the logic for reading the sensor, filtering the data and transmitting this information via the serial data circuit to the driver information center (DIC) for display. The temperature is sent to the IPC in degrees Celsius. The IPC is responsible for displaying the temperature and converting to degrees Fahrenheit if necessary. Two serial data signals are ultimately generated. An unfiltered value and a filtered value for use by the DIC display. The BCM also provides the sensor out-of-range detection and compensates for engine temperature by utilizing vehicle speed and engine off time duration.