Boiler Fault Code Error 03

Also written as ERROR03 — same fault.

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

Fault code Error 03 appears across 1 boiler brand and 2 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 that the internal components are getting too hot, so it has safely shut itself down to prevent any damage. (As reported on Atag Premier)