In-Vehicle Temperature Sensor

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

If MSCAN-Bus inactiv/active then

• Fan on for 300 sec. then switch off.

If Power mode changes to 4, then

• Fan on for 300 sec. then fan off.

If Power mode changes to 6 and HVAC on, then

• Fan is on.

If Power mode changes to 6 and HVAC off, then

• Fan on for 15 sec, then fan off.

If fan off, then fan requested to be on, then

• Wait x sec before fan on.

If Power mode 7, then:

• Fan on regardless of HVAC on/off status.

Fan is not disabled during crank (Power mode 9)

The automatic temperature control (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 automatic temperature control (ATC) module monitors the signal voltage and defaults to a temperature of 20°C (68°F) if it goes out of the range 0.4 - 4.8 V:

• If the signal voltage is less than 0.4 V, the automatic temperature control (ATC) module assumes there is a short circuit to ground.
• If the signal voltage is more than 4.8 V, the automatic temperature control (ATC) module assumes there is an open circuit or a short circuit to battery.