Your boiler's internal computer has encountered a communication error or logic conflict, causing the system to stop working for safety.

System fault boiler electronics / basic controller

What causes this fault?

This fault occurs when the boiler's main control board and the front display panel lose the ability to talk to each other correctly. It is effectively a software 'crash' caused by a hardware failure, meaning the boiler can no longer verify that it is operating safely. The most common reason is an electrical component failure on the printed circuit board or a loose connection in the internal wiring.