BoilerFaultCodes 9U 233 High
Boiler Fault Code 9U 233
Also written as 9U233 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 9U 233 appears across 1 boiler brand and 12 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's internal computer is failing to communicate with its memory chip, meaning it cannot start because it has forgotten its specific configuration settings. (As reported on Worcester Bosch Greenstar 12i System)
Pick your boiler brand for the 9U 233 fix
Source
Information for the 9U 233 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026