Your boiler’s internal computer brain hasn't been programmed correctly, meaning it doesn't know which model it is and cannot start up.

Unconfigured printed circuit board (PCB)

What causes this fault?

This fault occurs when the boiler's main control board has lost its identity or was never properly told which model it is installed in. It usually happens after a power surge scrambles the memory or if a new part was installed without the specific configuration chip being inserted. Without this digital profile, the boiler cannot safely coordinate the fan and gas valve, so it shuts down as a precaution.