Your boiler's main internal computer has encountered a critical error and is unable to operate the system safely.

There is an internal fault in the Automatic Control Module.

What causes this fault?

This fault occurs when the boiler's central control unit suffers an internal electronic failure, meaning it can no longer safely monitor or manage the heating process. It is often caused by damaged circuitry or a component failure within the module itself, which prevents the boiler from communicating with sensors and valves. Essentially, the boiler's 'brain' has stopped working correctly, and it shuts down to prevent any unsafe operation.