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

Fig 1: Engine Coolant Temperature Sensor Circuit - Circuit Diagram

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

For a complete wiring diagram, refer to appropriate SYSTEM WIRING DIAGRAMS article.

Theory of Operation 

The engine coolant temperature 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. (i.e. 2 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.