Your boiler's internal computer has detected a communication error or a hardware failure within its own electronic control system.

Internal fault

What causes this fault?

This fault occurs when the boiler's main control board suffers a hardware failure or a breakdown in its internal communication lines. It is essentially a software crash or an electronic malfunction that prevents the boiler from safely processing instructions. The most common reason is age-related component fatigue on the circuit board or a loose connection in the internal wiring harness.