dP Low

Boiler Fault Code dP

Also written as DP — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code dP appears across 2 boiler brands and 4 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 in a manual testing mode used by engineers to check emissions, rather than experiencing a genuine breakdown. (As reported on Biasi Concept 400 20 1 Mfs)

Pick your boiler brand for the dP fix

Biasi dP 3 models Johnson Starley dP 1 model

Source

Information for the dP fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026