P0125 Honda Accord
Insufficient Coolant Temperature for Closed Loop · Powertrain Code · Medium · Repair: Moderate
What is P0125?
The engine is not reaching operating temperature quickly enough for the ECM to enter closed-loop fuel control. Usually caused by a stuck-open thermostat.
When the Honda Accord triggers code P0125 (insufficient coolant temperature for closed loop), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Honda Accord.
This repair is rated moderate, meaning some experience and specialty tools required.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Honda Accord.
Common Causes on Honda Accord
- Stuck-open thermostat preventing engine from reaching operating temperature
- Failed ECT sensor reading lower than actual temperature
- Low coolant level affecting temperature sensor reading
- Thermostat housing gasket leak
Symptoms
- Check Engine Light on
- Engine takes very long to warm up
- Heater blows lukewarm air
- Poor fuel economy from open-loop fueling
- Temperature gauge stays low
Notes for Honda Accord
Honda thermostats commonly stick open around 100k miles — a $15 part that causes significant fuel economy loss if ignored.