Coolant Temperature Sensor/Switch (For Computer): Description and Operation

Coolant And Charge Temperature Sensors:

The coolant temperature sensor is installed in the thermostat housing where it maintains constant contact with the engine coolant. The engine controller sends out a reference voltage of approximately five (5) volts to the coolant temperature sensor. As coolant temperature changes, the internal resistance of the sensor will change, causing a voltage drop across the sensor. The engine controller reads the voltage drop across the sensor, and therefore the engine temperature.

The engine controller uses this information to adjust the air/fuel ratio being delivered to the engine.