Code
P0125
Cooling
Insufficient coolant temperature for closed-loop fuel control
The engine did not reach the temperature needed to switch to closed loop in time.
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Most likely causes
- Thermostat stuck open
- Low coolant level
- Faulty coolant temperature sensor
Symptoms you may notice
- Check engine light
- Engine runs rich and inefficient until "warm"
- Weak heater
Checks to run
- Verify coolant temperature reaches about 90 °C
- Test the thermostat
- Check coolant level
Tools you may need
OBD-II scanner
Infrared thermometer
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.