The Engine Coolant Temperature (ECT) Sensor responds to change in Engine Coolant Temperature. By measuring engine coolant temperature, the ECM (Engine Control Module) knows the average temperature of the engine and tells the computer what the engine temperature is so that optimum driveability is realized while the engine is warming up and when the engine has reached operating temperature. The following schematic shows a typical circuit diagram of the Engine Coolant Temperature (ECT) Sensor.
The ECT usually located in a coolant passage just before the thermostat. The ECT is connected to the THW terminal on the ECM. The ECT sensor is critical to many ECM functions such as fuel injection, ignition timing, variable valve timing, fuel and emission controls function, transmission shifting, and to turn the radiator-cooling fan on and off as needed.