Engine Coolant Temperature sensor

Engine Coolant Temperature Sensor (ECT) respond to change in engine coolant temperature, by measuring engine coolant temperature. The ECU know the average of the engine. the ECT  is usually located to the thermostat the ECT is connected to the THM terminal of ECU.

The ECT sensor is critical to many ECM functions, such as fuel injection, ignition, timing, variable valve, timing , transmission shifting etc. We have always check to if the engine at operating temperature and that the ECT is accuratly repeating the temperature to the ECU.

The engine coolant temperature sensor in container of water as shown.





WATER TEMPREATURE                        RESISTANCE

20 degree                                                        2.2 k ohms

30 degree                                                        1.8 k ohms

35 degree                                                        1.5 k ohms

40 degree                                                        1.2 k ohms

50 degree                                                        800 ohms

60 degree                                                        600 ohms

70 degree                                                       400 ohms 

80 degree                                                       300 ohms

85 degree                                                       300 ohms    

Plot resistance and temperature on the graph below.

Low temperature = High resistance and high voltage.

High temperature = Low resistance and voltage.

 

Explain the internal operation of this sensor?

CTS thermistor that change the resistance as temperature of coolant change.

The resistance is high when the engine is cold as the engine is warm up the internal resistance of the sensor drop until it reaches a maximum valve when engine is normal operation.