Your boiler's computer memory is blank or incorrect, meaning it doesn't currently know how to operate itself.

PCB Programming - Unprogrammed state

What causes this fault?

This fault occurs when the boiler's main control board loses its identity and can no longer remember which specific model it is installed in. The most common reason is a electronic failure within the PCB itself or a loose Customer ID chip, which acts like a small memory stick that tells the boiler how to function safely.