P0125

Insufficient Coolant Temperature for Closed Loop Fuel Control

Q: Is it safe to drive with P0125?

Yes. The engine runs normally; you'll just get less cabin heat and slightly worse economy while it runs cooler than ideal. Fix it at your convenience.

Q: Can I just clear P0125?

It returns until the engine can warm up properly. A stuck-open thermostat is the usual cause, so replacing it before clearing typically solves it.

Engine cooling / fuel control Generic OBD-II High

What it means

P0125 means the engine isn't reaching the coolant temperature it needs to switch into closed-loop fuel control within the expected time. The engine still runs and drives normally — you'll mainly notice weak cabin heat and slightly worse economy. A thermostat stuck open is by far the most common cause, followed by a faulty coolant temperature sensor.

High

Can I keep driving? Yes — the engine runs fine; it's just taking too long to warm up, so you'll mainly notice weaker cabin heat and slightly worse fuel economy until it's fixed.

Real-world scan data

Seen in

103

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Cabin heater blows cool or takes a long time to warm up
Slightly worse fuel economy
Temperature gauge slow to reach normal or reads low

Common causes

Most likely first

Thermostat stuck open — the most common causeLikely
Faulty engine coolant temperature (ECT) sensorCommon
Low coolant levelCommon
Wiring or connector fault at the ECT sensorLess often
Faulty ECM (rare)Less often

How to diagnose & fix

Work through it in order

Check coolant level and top up if low.
Watch coolant temperature on a scan tool during warm-up to see if it reaches operating temp.
Replace the thermostat if it's stuck open — the usual fix.
Test the ECT sensor and its wiring/connector.
Clear the code and confirm the engine reaches normal temperature.

FAQ

Quick answers

Is it safe to drive with P0125?+

Yes. The engine runs normally; you'll just get less cabin heat and slightly worse economy while it runs cooler than ideal. Fix it at your convenience.

Can I just clear P0125?+

It returns until the engine can warm up properly. A stuck-open thermostat is the usual cause, so replacing it before clearing typically solves it.

Read & clear P0125 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX