P0125-INSUFFICIENT COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL
P0125-INSUFFICIENT COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
The Engine Coolant Temperature (ECT) Sensor is a negative temperature coefficient thermistor-type sensor whose resistance varies inversely with temperature. At cold temperatures the sensor resistance is high so the voltage is high. As the coolant temperature increases the resistance decreases and the voltage becomes low. The INSUFFICIENT COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL determines if the engine coolant temperature will reach the closed loop fueling control temperature limit in a regulated time after start.
When Monitored:
With battery voltage greater than 10.4 Volts and after engine is started.
Set Condition:
The engine temperature does not go above -10°C (15°F). Failure time depends on start-up coolant temperature and ambient temperature. For example, two minutes for a start temp of -10°C (15°F) or up to 10 minutes for a vehicle with a start-up temp of -28°C (5°F). Two Trip Fault. Three good trips to turn off the MIL.
It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
NOTE:
If an 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. Make sure 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. Failure to follow these instructions can result
in possible serious or fatal injury. Allow the engine to cool before
opening the cooling system.
1.
Inspect the coolant system for proper level and condition.
This test works best if performed on a cold engine (cold soak)
1.
Ignition on, engine not running.
2.
Using the scan tool, read the Engine Coolant Temp Degree 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.
3.
Start the Engine.
4.
During engine warm-up monitor the Engine Coolant Temp Degree 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 scan tool Engine Coolant Temp Degree values should stay relatively close to each other.
5.
Using the appropriate Service Information, determine the proper opening temperature of the thermostat.
Did the thermostat open at the proper temperature?
Using the scan tool, read the Engine Coolant Temp Degree value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a 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.
3.
Start the Engine.
4.
During engine warm-up monitor the Engine Coolant Temp Degree 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 scan tools Engine Coolant Temp Degree value should stay relatively close to each other.
Is the thermometer reading relatively close to the scan tool ECT reading?