Boiler Fault Code 00:4

Also written as 004 — same fault.

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

Fault code 00:4 appears across 1 boiler brand and 6 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's internal settings are currently configured to manage your home heating zones and hot water separately, which is a normal state for this model rather than a sign of a mechanical failure. (As reported on Viessmann Vitodens 333)