High
9U 233 on Worcester Bosch 30i Junior

Your boiler's main internal computer has lost communication with its identification chip, meaning the system cannot safely operate or provide heating and hot water.

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) error – problem with code plug

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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