BoilerFaultCodesYour boiler's internal computer has encountered a critical communication error and cannot operate safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked
What causes this fault?
This fault occurs when the boiler's internal computer brain loses its connection with the specific data chip that holds its operating instructions. It is usually caused by a physical failure of the Heat Control Module chip or a breakdown in the electrical circuits on the main control board. Because the boiler no longer knows its own safety limits, it shuts down immediately to prevent damage.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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