BoilerFaultCodes 9U High
Boiler Fault Code 9U
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 9U appears across 2 boiler brands and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's main control computer is unable to communicate with its internal memory chip, meaning it cannot access the settings needed to run safely. (As reported on Ideal Maximiser SE)
Pick your boiler brand for the 9U fix
Source
Information for the 9U 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