BoilerFaultCodes 393 High
Boiler Fault Code 393
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 393 appears across 2 boiler brands and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning A sensor that checks the temperature of the boiler's exhaust gases has sent a faulty signal, so the boiler has most likely stopped as a precaution until a qualified engineer checks it. (As reported on Viessmann Vitodens 050-W B0HA-19)
Pick your boiler brand for the 393 fix
Source
Information for the 393 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 31 August 2026