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

Engine Coolant Temperature (ECT) Sensor






(1) ECT Electrical Connector
(2) Connector Tab
(3) Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor is a thermistor (a resistor which changes the value which is based on the temperature) mounted in the engine coolant stream. The low coolant temperature produces a high resistance (100,000 ohms at -40�C/-40�) while a high temperature will cause a low resistance (70 ohms at 130�C/266�F).

The PCM supplies a 5 volt signal to the engine coolant temperature (ECT) sensor 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. The engine coolant temperature affects the fuel control and the glow plug system.