BoilerFaultCodes D.118-4 Emergency
Boiler Fault Code D.118-4
Also written as D1184 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.118-4 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 has detected an inconsistency in its internal temperature readings, suggesting a potential issue with a safety sensor that prevents it from firing safely. (As reported on Vaillant ecoTEC exclusive)
Pick your boiler brand for the D.118-4 fix
Source
Information for the D.118-4 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