Your boiler is having trouble communicating with its internal control modules or multiple boiler system systems, which may stop it from operating correctly.

What causes this fault?

This fault occurs when the boiler's brain loses contact with the internal communication modules that coordinate its heating tasks. The most common reason is a loose or damaged wiring connection between internal components, or a electronic failure within the communication module itself. Essentially, the different parts of the boiler can no longer 'talk' to each other to confirm it is safe and ready to fire up.