Your boiler's internal computer has forgotten its settings or has developed a technical communication error, meaning it cannot safely control the heating process.

Printed circuit board (PCB) unconfigured or fault

What causes this fault?

This fault occurs when the boiler's central control board loses its identity or suffers a data communication failure, preventing it from managing the gas valve and pumps. The most common reason is a hardware failure within the motherboard or a missing configuration chip, which acts like a memory card telling the boiler exactly which model it is. It can also be triggered by a sudden power surge or electrical interference that corrupts the board's stored settings.