P0125 - Insufficient Coolant Temp For Closed-Loop Fuel Control: Notes

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.

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Refer to Pre-Diagnostic Troubleshooting Procedure .