Air Temperature Sensor ( Ambient / Intake ): Description and Operation

AIR TEMPERATURE SENSORS

The air temperature sensor is a 2 wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
- Ambient
- Inside
- Duct

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 decreases as the resistance decreases. The sensor operates within a temperature range between -40 to +150°C (-40 to +300°F). The sensor signal varies between 0-5 volts. The IPM converts the signal to a range between 0-255 counts.

The IPM uses the sensor signals to determine the air temperature door position. Left and right air temperature sensor inputs in a dual zone HVAC system are used to adjust the corresponding left and right air temperature door. In HVAC systems with upper and lower duct temperature sensors, the IPM uses the following sensor inputs with the indicated mode positions:

If the IPM detects a malfunctioning sensor, then the control module software will use a defaulted air temperature value. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.

The scan tool has the ability to update the displayed ambient air temperature.