Boiler Fault Code 2 nn

Also written as 2NN — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code 2 nn appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is attempting to light the flame but failing to successfully detect that it has started, which means it will keep trying until it eventually locks out for safety. (As reported on Keston C40)