BoilerFaultCodes D.090 Medium
Boiler Fault Code D.090
Also written as D090 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.090 appears across 1 boiler brand and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is having trouble communicating with its external controller or smart thermostat, which is preventing it from receiving proper instructions to heat your home. (As reported on Vaillant ecoTEC plus)
Pick your boiler brand for the D.090 fix
Source
Information for the D.090 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