BoilerFaultCodes D.003 Low
Boiler Fault Code D.003
Also written as D003 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.003 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 simply reporting the current temperature of the water leaving it, which is a normal part of its internal monitoring process rather than a fault. (As reported on Vaillant ecoTEC Pro 28)
Pick your boiler brand for the D.003 fix
Source
Information for the D.003 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