Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Engine Coolant Temperature SensorA thermistor that is built into the engine coolant temperature sensor changes the resistance value according to the engine coolant temperature.
The lower the engine coolant temperature sensor, the greater the thermistor resistance value, and the higher the engine coolant temperature sensor temperature, the lower the thermistor resistance value.
The engine coolant temperature sensor is connected to the ECM. The 5 V power source voltage in the ECM is applied to the engine coolant temperature sensor from the terminal THA via a resistor R. That is, the resistor R and the engine coolant temperature sensor are connected in series.
When the resistance value of the engine coolant temperature sensor changes in accordance with changes in the engine coolant temperature, the potential at terminal THA also changes. Based on this signal, the ECM increases the fuel injection volume to improve driveability during cold engine operation.