Boiler Fault Code D.118 (14)

Also written as D11814 — same fault.

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

Fault code D.118 (14) 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 an electrical issue with its internal carbon monoxide monitoring system, causing the safety system to shut down to prevent incorrect readings. (As reported on Vaillant ecoTEC exclusive)