Circuit Operation

5 volts current is applied to the engine coolant temperature sensor output terminal (terminal 1) from the ECM (terminal 83 - M/T) or PCM (terminal 44 - A/T) via the resistor in the ECM (M/T) or PCM (A/T). The ground terminal (terminal 2) is grounded with ECM (terminal 92 - M/T) or (terminal 57 - A/T).
The engine coolant temperature sensor is a negative temperature coefficient type of resistor. It has the characteristic that when the engine coolant temperature rises, the resistance decreases.
The engine coolant temperature sensor output voltage increases when the resistance increases and decreases when the resistance decreases.