BoilerFaultCodes D.171 Medium
Boiler Fault Code D.171
Also written as D171 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.171 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 struggling to detect the correct water pressure inside the system, which may be caused by a sensor issue or an imbalance in the water levels. (As reported on Vaillant ecoTEC plus)
Pick your boiler brand for the D.171 fix
Source
Information for the D.171 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