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

Coolant Temperature Sensor (Typical):

The Coolant Temperature Sensor (CTS) 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 varying voltage drop across the sensor. The engine controller reads the voltage drop across the sensor, and therefore the engine temperature, by the amount of voltage drop across the sensor.

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.