Engine Temperature Sensor: Description and Operation

Engine coolant temperature (ECT) sensor
Located at the side of intake manifold or on the coolant outlet pipe, this sensor measures the temperature of the engine coolant and converts its change into that in resistance through the thermistor.

By monitoring the resistance of the coolant temperature sensor, ECM (PCM) detects the engine coolant temperature and that affects most systems under the control of ECM (PCM).