Toyota Diesel Engine Coolant Temperature Sensor

Working principle of the ECT sensor
In order to convert the ECT resistance variation to voltage variation, which is further processed by the ECU, the ECT sensor is connected in a circuit typically supplied with a reference voltage of +5V. In cold engine and an ambient temperature of 20 ?C the sensor resistance is between 2000? and 3000?. After the engine start, coolant temperature begins to rise. ECT gradually heats and its resistance reduces proportionately. At 90 ?C its resistance is in the range of 200? to 300?.
Thereby, a coolant temperature dependent variable voltage signal is send to the onboard computer.