dP Low

Biasi dP Fault Code

Also written as DP — same fault.

The Biasi dP fault code means: your boiler is currently running a manual test mode to check the flue and emissions, and it's not actually broken.. It appears on 2 Biasi models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: chimney sweep function at maximum output in domestic hot water mode
Typical repair cost £0 (including labour)

DIY fix possible

Wait up to 15 minutes for the test cycle to finishPress the 'Reset' button to manually exit the test modeTurn the mode selector dial away from the chimney sweep icon

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Biasi models that show the dP fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Biasi dP fault code information on this page is sourced and cross-checked against the official Biasi service / installation manuals for each affected model.

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