BoilerFaultCodes D.70 Low
Boiler Fault Code D.70
Also written as D70 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code D.70 appears across 2 boiler brands and 21 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 stuck in a diagnostic test mode that overrides its normal settings, which usually happens during a service or repair. (As reported on Vaillant ecoTEC)
Pick your boiler brand for the D.70 fix
Source
Information for the D.70 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