Error code

OBD2 P0125

OBD2P0125
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Insufficient Coolant Temperature for Closed Loop Fuel Control.

Severity

moderateCan drive, but expect reduced fuel efficiency and performance.

Summary

P0125 indicates that the engine coolant temperature is insufficient for closed loop fuel control, typically due to issues with the cooling system or sensors.

Symptoms

  • Decreased fuel economy
  • Decreased engine performance

Common Causes

  • Faulty AFR sensor
  • Cold weather conditions
  • Low coolant level or leaks in the cooling system
  • Broken thermostat allowing constant coolant flow
  • Faulty ECT sensor or wiring issues

Diagnosis

  1. Check coolant level and condition of the cooling system for leaks.
  2. Verify thermostat operation using a thermometer or scan tool.
  3. Inspect AFR sensor readings with a scan tool to ensure proper fluctuation.
  4. Test ECT sensor circuit for corrosion or faults.

Fixes

  • Replace faulty AFR sensor
  • Add coolant and check for leaks in the cooling system
  • Install a new thermostat if it is stuck open or broken
  • Replace faulty ECT sensor

FAQ

What should I do if my car has P0125 in cold weather?

Ensure the coolant level is correct and consider adding insulation or a block heater to help maintain engine heat.

How can I check if the thermostat is working properly?

Use a thermometer or scan tool to monitor radiator hose temperature after 10-15 minutes of driving. The hose should remain cool until the thermostat opens, then rapidly warm up.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

More OBD2 codes

All OBD2 codes →Search more codes →