P0125Medium urgency

Insufficient Coolant Temperature for Closed Loop

Engine · Cooling System

⚠️ Fix soon — engine is not reaching operating temperature.
What this means

The engine is taking too long to reach closed-loop fuel control temperature. Usually means the thermostat is stuck open, keeping the engine too cool. A cold-running engine burns more fuel and wears faster.

Likely causes
  • Thermostat stuck openMost common
  • Faulty coolant temp sensorCommon
  • Low coolant levelLess common
Estimated repair cost
Thermostat replacement$150 – $400
Coolant temp sensor$75 – $200
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Frequently asked questions

What does P0125 mean?

The engine is taking too long to reach closed-loop fuel control temperature. Usually means the thermostat is stuck open, keeping the engine too cool. A cold-running engine burns more fuel and wears faster.

Is P0125 serious?

Fix soon — engine is not reaching operating temperature.

How much does it cost to fix P0125?

Repair costs for P0125 range from $150 – $400 depending on the root cause and your vehicle.

Can I drive with P0125?

You can drive short distances but should have it repaired within 1-2 weeks to prevent further damage.