Your boiler's internal computer has encountered a software or hardware communication error, preventing it from starting up correctly.

System fault boiler electronics / basic controller

What causes this fault?

This fault occurs when the boiler's internal computer chips fail to communicate or 'handshake' with each other during the start-up sequence. It is usually caused by a physical hardware failure on the main circuit board or a loose connection in the internal wiring. Essentially, the boiler's brain has encountered a critical error that prevents it from safely managing the heating process.