What does code P0125 mean?

P0125 — Coolant temperature isn't rising fast enough to enter closed-loop fuel control. Engine takes forever to warm up, ECM stays in enriched open-loop — fuel economy tanks. Belongs to the powertrain.coolant system. Severity: warning.

What are the common causes of P0125?

Thermostat stuck open — main cause in winter; Low coolant level or slow leak; Faulty ECT sensor reading low; Cooling fan running constantly due to bad relay; Clogged radiator giving too much cooling

Can I drive with code P0125?

Limited: reaching the nearest workshop is fine, but avoid long trips. May progress into a more serious fault.

How do I diagnose P0125?

Read the code and freeze-frame with a scanner, check related-system errors, inspect the components listed (wiring, connectors, sensors). See the "How to diagnose" section above for the full step-by-step.

How do I clear code P0125?

The code can be cleared via an OBD-II scanner (e.g. ELM327 + the Car Diagnostics app): plug the adapter into the OBD port, go to Errors → Clear. If the underlying cause isn't fixed, the code will return within a few drive cycles.

OBD-II Code P0125 — Car Diagnostics Platform

What it means

Common causes

Thermostat stuck open — main cause in winter
Low coolant level or slow leak
Faulty ECT sensor reading low
Cooling fan running constantly due to bad relay
Clogged radiator giving too much cooling
Miscalibrated ECM after installing a non-OEM thermostat

How to diagnose

01
Read all stored and pending codes with an OBD-II adapter — get the full picture, not just the one code.
02
Capture freeze-frame data (RPM, coolant temperature, engine load) at the exact moment the code triggered.
03
Inspect the named subsystem with our app's AI explanation — get vehicle-specific causes for your make, model and year.

Decode P0125 on your actual car

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