Your boiler has detected a potential issue with the valve that controls the gas supply, meaning it isn't shutting off correctly for safety.

Burner in fault state. Fuel valve closes too late. Cause: Check gas combination valve. Check both control paths. Press E.

What causes this fault?

This fault occurs when the boiler's internal computer detects that gas is still flowing for a few seconds after the burner was supposed to switch off. The most common reason is a mechanical failure within the gas valve itself, where it becomes 'sticky' and fails to snap shut instantly, or a fault in the electronic control board that manages the safety sequence.