BoilerFaultCodes D.023 Low
Boiler Fault Code D.023
Also written as D023 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.023 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 currently performing a routine check to ensure the heating system has enough water flow before it ignites, which is a normal part of its operation. (As reported on Vaillant ecoTEC Pro 24)
Pick your boiler brand for the D.023 fix
Source
Information for the D.023 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