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

Coolant Temperature Circuit:

Purpose:
The CTS allows the ECM to monitor temperature of engine coolant. Engine coolant temperature affects the cold advance and glow plug systems.

Operation:
The coolant temperature sensor is a thermistor which changes value based on temperature. Low coolant temperature produces a high resistance, while high temperature results in low resistance.

The ECM supplies a 5 volt signal to the coolant sensor, through a resistor in the ECM and measures the voltage. The voltage will be high, when the engine is cold, and low when the engine is hot. By measuring the voltage, the ECM knows the engine coolant temperature.

Location:
The CTS is mounted in the engine coolant stream.