BoilerFaultCodes Er03 High
Boiler Fault Code Er03
Also written as ER03 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Er03 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's internal computer is experiencing a communication error and has shut down for safety, meaning you currently have no heating or hot water. (As reported on Biasi Concept 400 20 1 Mfs)
Pick your boiler brand for the Er03 fix
Source
Information for the Er03 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 7 July 2026