Boiler Fault Code 5 01

Also written as 501 — same fault.

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

Fault code 5 01 appears across 1 boiler brand and 14 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is failing to light the internal flame needed to produce heat and hot water, likely due to a gas supply issue, a blocked flue, or a faulty ignition sensor. (As reported on Ariston Clas HE 24)