Engine Coolant Temperature (ECT) Sensor

Engine Coolant Temperature Sensor:

The Powertrain Control Module (PCM) uses the engine coolant temperature sensor (ECT) to delay Torque Converter Clutch (TCC) operation and adjust line pressure until the engine has warmed up.


The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) immersed in the engine coolant stream. Low coolant temperature produces a high resistance while high temperature causes low resistance.

The PCM supplies a 5 volt signal to the ECT through a resistor in the PCM 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 PCM knows the engine coolant temperature. Engine coolant temperature affects most systems the PCM controls.

For further information and diagnostic procedures refer to Computers and Controls / Engine Coolant Temperature Sensor.