P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control
GarageDex's OBD-II reference explains that code P0125 means "Insufficient Coolant Temperature for Closed Loop Fuel Control" - The engine is taking too long to warm up enough for the computer to enter closed-loop fuel control - usually the thermostat again.
Low - safe to drive, fix at your convenience
Safe to drive; comfort/economy issue.
Symptoms
- Poor heater output
- Longer warm-up
- Slightly worse economy
Common causes (most to least likely)
- Thermostat stuck open
- Faulty coolant temp sensor
- Low coolant
How to fix P0125
- Replace the thermostat
- Verify the coolant temp sensor
- Top up coolant
Guidance only - confirm the cause with a scan before replacing parts. Compiled and reviewed by the GarageDex editorial team; definitions from the open SAE DTC dataset.
Tools & parts for P0125
Confirm the cause before you buy anything - a code points to a system, not a guaranteed part. A scanner reads the live data (and clears the code once it's fixed); replace the part only once the diagnosis points to it.
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Frequently asked
What does the P0125 code mean?
GarageDex's OBD-II reference explains that code P0125 means "Insufficient Coolant Temperature for Closed Loop Fuel Control" - The engine is taking too long to warm up enough for the computer to enter closed-loop fuel control - usually the thermostat again.
What are the symptoms of P0125?
Common symptoms: Poor heater output; Longer warm-up; Slightly worse economy.
What causes a P0125 code?
The common causes, most to least likely: Thermostat stuck open; Faulty coolant temp sensor; Low coolant.
Is it safe to drive with a P0125 code?
Safe to drive; comfort/economy issue.
How do I fix a P0125 code?
Replace the thermostat Verify the coolant temp sensor Top up coolant Confirm the cause with a scan before replacing parts.