High Lockout
360 on Worcester Bosch CDi Classic

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

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.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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