Boiler Fault Code Block 01

Also written as BLOCK01 — same fault.

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

Fault code Block 01 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 has been automatically shut down because an external safety device, such as a separate room thermostat or a smoke alarm link, has triggered a signal to stop the system. (As reported on Atag E Range)