Boiler Fault Code dU

Also written as DU — same fault.

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

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

Most common meaning Your boiler is currently set to a specific maintenance mode used by engineers to replace internal parts, rather than being in a fault state. (As reported on Ideal Logic Code Combi ESP1)