BoilerFaultCodes D.172 Medium
Boiler Fault Code D.172
Also written as D172 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.172 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 monitoring a mismatch between the desired temperature and the actual temperature of the water flowing through your heating system. (As reported on Vaillant ecoTEC plus)
Pick your boiler brand for the D.172 fix
Source
Information for the D.172 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