BoilerFaultCodes 9U233 High
Boiler Fault Code 9U233
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 9U233 appears across 1 boiler brand and 3 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 memory chip is having trouble communicating, which has caused the system to shut down for safety. (As reported on Worcester Bosch Greenstar Si Combi / i System)
Pick your boiler brand for the 9U233 fix
Source
Information for the 9U233 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