Boiler Fault Code 34:1

Also written as 341 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code 34:1 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 is confused by an external signal telling it to run the heating pump, which may be caused by a faulty control module or a wiring problem. (As reported on Viessmann Vitodens 300-W)