BoilerFaultCodes E 91 Medium
Boiler Fault Code E 91
Also written as E91 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code E 91 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 is temporarily limiting its performance because it has detected a reading that suggests the air mixture is not quite right, often triggered by flue conditions or pressure changes. (As reported on Warmhaus Enerwa)
Pick your boiler brand for the E 91 fix
Source
Information for the E 91 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