In-Vehicle Temperature Sensor

WARNING: This page is about a different car, the 2006 Land Rover Range Rover. However, it is still accessible from the selected car via links, so may be relevant.

The in-vehicle temperature sensor is an encapsulated negative temperature coefficient (NTC) thermistor that provides the ATC module with an input of passenger compartment air temperature. The in-vehicle temperature sensor is installed behind a grille in the ATC module control panel. An electric fan in the ATC module runs continuously, while the ignition is on, to draw air through the grille and across the in-vehicle temperature sensor.

The ATC module uses the signal from the in-vehicle temperature sensor for control of the coolant temperature valve(s), blower speed and air distribution.

The signal voltage from the in-vehicle temperature sensor is between 0 and 5 V. The ATC module monitors the signal voltage and defaults to a temperature of 20°C (68°F) if it goes out of the range 0.573 - 4.882 V:

If the signal voltage is less than 0.573 V, the ATC module assumes there is a short circuit to ground.
If the signal voltage is more than 4.882 V, the ATC module assumes there is an open circuit or a short circuit to battery.