BoilerFaultCodes C5 High
Boiler Fault Code C5
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code C5 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 having trouble communicating with its internal pump, which means it cannot properly move heated water around your system. (As reported on Viessmann Vitodens 200)
Pick your boiler brand for the C5 fix
Source
Information for the C5 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