DTC P0125: Insufficient Coolant Temperature For Closed Loop Fuel Control: Operation

A 5-volt voltage is applied to the ECT sensor output terminal (terminal No. 1) from the PCM terminal No. 44 via the resistor in the PCM. The ground terminal (terminal No. 2) is grounded with PCM (terminal No. 57). The ECT sensor is a negative temperature coefficient type of resistor. It has the characteristic that when the engine coolant temperature rises the resistance decreases. The ECT sensor output voltage increases when the resistance increases, and decreases when the resistance decreases. See Figure .