Your boiler's computer chip has failed or is recognized as incorrect, meaning the main brain of the boiler cannot talk to its control board.

Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box

What causes this fault?

This fault occurs when the boiler's memory chip, known as the Heat Control Module, becomes corrupted or suffers an electrical failure. The main control board effectively loses its identity and can no longer safely manage the heating process, causing the system to shut down for safety. Most often, this is the result of a sudden power surge or simple component degradation over time.