BoilerFaultCodes E:04.00 High
Boiler Fault Code E:04.00
Also written as E0400 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code E:04.00 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 failing to detect the gas supply needed to start a flame, meaning it cannot produce heating or hot water until the issue is addressed. (As reported on Baxi Combi 224, 228, 424, 428)
Pick your boiler brand for the E:04.00 fix
Source
Information for the E:04.00 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