BoilerFaultCodes D.163 Medium
Boiler Fault Code D.163
Also written as D163 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.163 appears across 1 boiler brand and 3 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 issue with an external add-on component, such as an external pump or secondary heating controller, which is preventing it from operating as intended. (As reported on Vaillant ecoTEC plus)
Pick your boiler brand for the D.163 fix
Source
Information for the D.163 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