B Low

Baxi B Fault Code

The Baxi B fault code means: your boiler has entered a special test or setup mode, which usually happens during a service or when a heating engineer is calibrating the system.. It appears on 5 Baxi 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: Switch to DHW mode maximum flow & press reset

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Baxi models that show the B fault code

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

Source

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

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