Insufficient Coolant Temperature for Closed Loop Fuel Control
The engine has been running long enough that it should be in closed-loop fuel control, but the ECU never sees the coolant reach the expected temperature. Almost always a thermostat that is stuck open.
Indicación de gravedad: Baja: normalmente sin impacto en la conducción, resuélvalo en la próxima revisión
Síntomas que notará
- Heater blows lukewarm
- Temperature gauge below normal
- Higher fuel consumption
- Emissions test failure
Causas habituales
Ordenadas de más a menos probable: empiece por arriba.
- 1 Thermostat stuck open
- 2 Failed coolant temperature sensor reading low
- 3 Very cold ambient use with a short journey cycle
Cómo diagnosticarlo
Primero lo más barato y menos invasivo: la mayoría de estos códigos no son un problema de piezas.
- ✓ Watch ECT on a scan tool during a 10-minute drive; it should stabilise around 85–95 °C.
- ✓ Feel the upper and lower radiator hoses — both getting warm early means the thermostat is open.
- ✓ Compare ECT with a infrared thermometer on the housing.
Opciones de reparación
- Replace the thermostat
- Replace the ECT sensor if it reads implausibly low
- Bleed the cooling system
P0125 — preguntas frecuentes
Is this urgent? +
Not mechanically urgent, but running rich long-term damages the catalytic converter and washes oil films off cylinder walls.
Could it just be a cold day? +
In sub-zero conditions with short trips, yes — confirm with a longer drive before replacing parts.
Confirme el diagnóstico antes de comprar piezas
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