Circuit/System Description
Air Temperature Sensors
The air temperature sensors are a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
* Ambient Air Temperature Sensor
* Inside Air Temperature Sensor Assembly
* Upper Left Air Temperature Sensor
* Upper Right Air Temperature Sensor
* Lower Left Air Temperature Sensor
* Lower Right Air Temperature Sensor
* Upper Auxiliary Air Temperature Sensor
* Lower Auxiliary Air Temperature Sensor
* Auxiliary Inside Air Temperature Sensor
A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance
decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40 to +101锟斤拷C
(-40 to +215锟斤拷F). The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts. As the
air temperature increases the count value will decrease. If the HVAC control module or auxiliary HVAC control module detects a malfunctioning
sensor, then the control module software will use a defaulted air temperature value. The default value for the ambient and inside air temperature
sensors will be displayed on the scan tool. The default value for the duct air temperature sensors will not be displayed on the scan tool. The scan tool
parameter for the duct air temperature sensors are the actual state of the signal circuit. The default action ensures that the HVAC system can adjust
the inside air temperature near the desired temperature until the condition is corrected.
