BoilerFaultCodes 405 High
Boiler Fault Code 405
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 405 appears across 1 boiler brand and 2 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 has encountered a critical electronic error and can no longer control the heating system safely. (As reported on Ideal Ideal Classic SE15P FF)
Pick your boiler brand for the 405 fix
Source
Information for the 405 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