How much does it cost to fix boiler error code D.012?

Typical repair cost for the boiler D.012 fault is £150-250 including labour.

D.012 Medium

Boiler Fault Code D.012

Also written as D012 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code D.012 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 signalling that the internal pump responsible for sending hot water to your separate hot water cylinder is currently not operating as expected. (As reported on Vaillant ecoTEC Pro 30)

Pick your boiler brand for the D.012 fix

Vaillant D.012 7 models

Source

Information for the D.012 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