BoilerFaultCodes D.170 Medium
Boiler Fault Code D.170
Also written as D170 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.170 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 is currently stuck in a specific operational mode while it attempts to communicate with an external control system, meaning it is not responding to your heating or hot water requests. (As reported on Vaillant ecoTEC Plus 836)
Pick your boiler brand for the D.170 fix
Source
Information for the D.170 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