Your boiler is having difficulty communicating with its internal smart connection module, usually meaning there is a minor electronic glitch or a connection has come loose.

What causes this fault?

This fault occurs when the boiler's internal brain loses touch with the communication module that allows it to talk to other smart devices or controls. It is usually caused by a loose connection following a recent service, or a small electronic failure where the internal wiring has become insecure. In some cases, it simply means the communication board has failed and needs replacing to restore the data link.