BoilerFaultCodes b7 257 High
Boiler Fault Code b7 257
Also written as B7257 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code b7 257 appears across 1 boiler brand and 1 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 electronic brain has encountered a serious internal error and can no longer safely operate your heating or hot water. (As reported on Worcester Bosch Greenstar i)
Pick your boiler brand for the b7 257 fix
Source
Information for the b7 257 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 31 August 2026