How much does it cost to fix Viessmann error code db?

Typical repair cost for the Viessmann db fault is £90-180 including labour.

db Low

Viessmann db Fault Code

Q: What does the Viessmann db fault code mean?

Your boiler has lost its connection to one of the temperature sensors used to control your heating, though it will likely keep running in a basic backup mode.

Also written as DB — same fault.

The Viessmann db fault code means: your boiler has lost its connection to one of the temperature sensors used to control your heating, though it will likely keep running in a basic backup mode.. It appears on 7 Viessmann models in our database.

Technical description: Control mode without room influence - Heating circuit M2 room temperature sensor shorted out

What causes the Viessmann db fault?

This fault occurs when the boiler loses a reliable signal from the sensor that monitors the temperature inside your living area. It is typically caused by a frayed or loose connection in the wiring, or a internal failure within the sensor itself, meaning the boiler no longer knows how warm your rooms actually are. Instead of shutting down completely, the system reverts to a basic setting to ensure you still have some heat.

Typical repair cost £90-180 (including labour)

Engineer required

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

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Viessmann models that show the db fault code

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

Source

Viessmann db 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