Your boiler has encountered an internal communication error between its main electronic control boards, meaning it cannot currently function or heat your home.

System fault boiler electronics / basic controller

What causes this fault?

This fault occurs when the boiler's two main 'brains'—the primary control board and the display board—stop talking to each other. It is usually caused by a loose internal connection, a glitch in the software, or a component failure on one of the electronic circuit boards. Think of it like a computer crashing because two internal parts can no longer share information.