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P0125

Schematic:




The engine coolant temperature (ECT) sensor is a thermistor that varies resistance according to changes in engine coolant temperature. The ECM supplies a five volt reference through a pull-up resistor to the sensor, which is connected to ground. When the sensor is cold it has a high resistance (high signal voltage at ECM). As the sensor temperature increases, its resistance decreases (lower signal voltage at ECM). The ECM uses the signal voltage to determine engine coolant temperature. DTC P0125 will set the if engine coolant temperature is a certain amount below a modeled temperature after a certain amount of air has gone through the engine. This indicates that the engine is running cooler than normal.

DTC PARAMETERS
DTC P0125 will set if engine coolant temperature is 10°C (50°F) below a modeled value at any one time based on engine airflow when:
^ Engine run time is between 2 and 5 minutes depending on engine airflow
^ No ECT sensor DTCs have been set

DTC P0125 runs continuously once the above conditions have been met.

DTC P0125 is a type B DTC

DIAGNOSTIC AIDS
DTC P0125 indicates lower than normal engine coolant temperature, which most likely was NOT caused by a short/open or intermittent short/open in the ECT wiring. Possible causes of low engine coolant temperature:
^ Thermostat stuck open
^ Cooling fans always On
^ Very low ambient temperatures
^ Corrosion in connector or resistance in wiring
^ Skewed sensor

Refer to ECT General Description for a Temperature vs. Resistance chart.