BoilerFaultCodes d.01 Low
Boiler Fault Code d.01
Also written as D01 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code d.01 appears across 1 boiler brand and 22 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 running its internal pump to move excess heat away from the system, which is a normal part of the cooling-down process after your heating or hot water has been active. (As reported on Vaillant ecoTEC plus Aquaplus)
Pick your boiler brand for the d.01 fix
Source
Information for the d.01 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 27 April 2026