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

Engine Coolant Temperature (ECT) Sensor:

The Engine Coolant Temperature (ECT) sensor (2) is located at the rear of the cylinder head in the thermostat housing (1). The ECT sensor is a thermistor, or a variable.resistor that changes value when the temperature changes. The ECT sensor is connected in series with a fixed resistor in the PCM.

The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage drop across the ECT sensor and converts the voltage reading into a temperature value. The ECT sensor voltage reading at the PCM will vary with the changes in the engine temperature.