Your boiler's internal computer system is currently confused and cannot communicate correctly, meaning the unit will not start until it is digitally reconfigured.

Boiler PCB configuration error. This may occur if the main PCB or display PCB is changed.

What causes this fault?

This fault occurs when the boiler's internal control boards fail to recognise each other or have conflicting information about how the unit should operate. The most common reason is that a replacement part has been installed but not correctly programmed to match your specific model, or a surge in the electrical supply has scrambled the memory on the circuit board.