Celica GT Liftback L4-2164cc 2.2L DOHC MFI (1998)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
A 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.
If the ECM detects the DTC P0115, it operates fail safe function in which the engine coolant temperature is assumed to be 80°C (176°F).
