Your boiler has detected an electrical fault in the system that controls the gas supply, meaning it cannot safely start up to provide heat or hot water.

Gas valve electrical error.

What causes this fault?

This fault occurs when the boiler's main control board loses proper electrical communication with the gas valve, which is the component responsible for releasing fuel into the burner. It is typically caused by a loose connection in the internal wiring, a moisture-related short circuit, or a mechanical failure within the gas valve's solenoid coils.