Possible Causes
LOW COOLANT LEVEL
THERMOSTAT OPERATION
ENGINE COOLANT TEMPERATURE SENSOR
DIAGNOSTIC PROCEDURE - P0125-INSUFFICIENT COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL
| TEST | ACTION |
|---|---|
| 1 |
NOTE:
If a Engine Coolant Temperature (ECT) DTC is set along with this code, diagnose the ECT DTC first.
NOTE:
Inspect the ECT terminals and related PCM terminals. Ensure the terminals are free from corrosion and damage.
NOTE:
The best way to diagnose this DTC is to allow the vehicle to sit overnight outside in order to have a totally cold soaked engine.
NOTE:
Extremely cold outside ambient temperatures may have caused this DTC to set.
WARNING:
Never open the cooling system when the engine is hot. The system is under pressure. Extreme burns or scalding may result. Allow the engine to cool before opening the cooling system. Check the coolant system to make sure that the coolant is in good condition and at the proper level.Is the coolant level and condition OK?
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| 2 |
NOTE:
This test works best if performed on a cold engine (cold soak). Ignition on, engine not running.With the DRBIII®, read the ECT Deg value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.
NOTE:
If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached. Start the Engine.During engine warm-up, monitor the ECT Deg value. The temp deg value change should be a smooth transition from start up to normal operating temp 82°C (180°F). Also monitor the actual coolant temperature with a thermometer.
NOTE:
As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the ECT Deg in the DRB sensor should stay relatively close to each other. Using the appropriate service information, determine the proper opening temperature of the thermostat.Did the thermostat open at the proper temperature?
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| 3 | Ignition on, engine not running. With the DRBIII®, read the ECT Sensor temperature value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.
NOTE:
If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached. Start the Engine. During engine warm-up, monitor the ECT Deg value. The temp deg value change should be a smooth transition from start up to normal operating temp 82°C (180°F). Also monitor the actual coolant temperature with a thermometer.
NOTE:
As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the ECT Sensor Temperature in the DRBIII® sensors should stay relatively close to each other. Is the thermometer reading relatively close to the DRBIII® ECT Sensor reading?
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