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

Coolant Temperature Sensor (Typical):

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 operating range of the coolant temperature sensor is -40°F to 265°F.

Based on the amount of voltage drop at the coolant sensor, the engine controller will:

^ Adjust the fuel injector pulse width. A cold engine will receive a longer pulse width, allowing for a richer mixture.
^ Monitor and adjust engine warm-up speed.
^ Turn ON the engine cooling fan.