BoilerFaultCodes ALL04 High
Boiler Fault Code ALL04
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code ALL04 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 has detected an internal electronic or sensor problem and has shut down as a safety precaution. (As reported on Sime iQE Simplicity 20T)
Pick your boiler brand for the ALL04 fix
Source
Information for the ALL04 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 7 July 2026