BoilerFaultCodesViessmann bd Fault Code
Also written as BD — same fault.
The Viessmann bd fault code means: your boiler has lost communication with your remote room thermostat or heating controller for the second heating circuit.. It appears on 7 Viessmann models in our database.
Technical description: Communication fault - Vitotrol remote control heating circuit M2. Control mode without remote control
What causes the Viessmann bd fault?
This fault occurs when the boiler's main internal computer loses its connection with the remote thermostat or controller managing your second heating circuit. The most common reason is an electrical break in the wiring between the units, a loose connection, or a hardware failure within the communication module itself.
DIY fix possible
Check if the batteries in your wall-mounted thermostat need replacingEnsure the thermostat is within signal range of the boilerTurn the boiler off and back on at the fused spur switch to reset the connection
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Gas Safe Register →Viessmann models that show the bd fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann bd fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026