تخلیه نشدن آب‌گیر در سرویس

The fuel filter's water trap left undrained, so separated water accumulates past the point where it is contained. The trap only protects the system while there is room in it — once full, water passes downstream to the high pressure pump.

It is a maintenance omission rather than a component fault, and its consequence is expensive: water in a high pressure diesel system removes the lubrication the pump depends on. The warning sensor exists to prevent exactly this and is often reset rather than acted on. Ask when the trap was last drained — many vehicles need it far more often than the filter is changed, and on some it is a scheduled item that garages skip because it is not visible on the invoice.