DTC P0125: Insufficient Engine Coolant Temperature For Closed Loop Fuel Control: Description

The engine coolant temperature sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the ECM. The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases. See Fig 1.

Fig 1: Engine Coolant Temperature Identification & Reference Data

Courtesy of NISSAN MOTOR CO., U.S.A.