Your boiler's electronic control board has detected an internal computer error and has shut down as a safety precaution.

Internal fault

What causes this fault?

These codes indicate that the boiler's central control board has suffered a critical software or hardware glitch, preventing it from managing the heating process safely. This usually happens because internal components on the circuit board have worn out or been damaged by a power surge, meaning the 'brain' of the boiler can no longer communicate with the sensors and valves. Because the board can no longer guarantee safe operation, it enters a protective shutdown mode.