How much does it cost to fix boiler error code S.56?

Typical repair cost for the boiler S.56 fault is £150-300 including labour.

S.56 Emergency

Boiler Fault Code S.56

Also written as S56 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code S.56 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected high levels of carbon monoxide and has automatically paused operation to keep you safe while it waits for the fumes to clear. (As reported on Vaillant ecoTEC exclusive)

Pick your boiler brand for the S.56 fix

Vaillant S.56 1 model

Source

Information for the S.56 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