BoilerFaultCodes 34:2 Medium
Boiler Fault Code 34:2
Also written as 342 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 34:2 appears across 1 boiler brand and 5 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 an unusual communication signal from an external control or pump, meaning the system is confused about when it should be running. (As reported on Viessmann Vitodens 300-W)
Pick your boiler brand for the 34:2 fix
Source
Information for the 34:2 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