Your boiler has detected an internal communication problem between its electronic components or a possible electrical connection fault.

check the wiring harness

What causes this fault?

This fault occurs when the boiler's main control centre loses the ability to talk to the internal components that regulate heat and safety. It is typically caused by a loose electrical connection, a damaged wiring loom, or a failure within the printed circuit board itself. Think of it like a loose cable on a computer that prevents the hardware from receiving instructions properly.