BoilerFaultCodesViessmann b0 Fault Code
Also written as B0 — same fault.
The Viessmann b0 fault code means: your boiler has detected an electrical fault with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.. It appears on 7 Viessmann models in our database.
Technical description: Burner blocked: Flue gas temperature sensor short circuit
What causes the Viessmann b0 fault?
This fault occurs when the boiler's internal computer detects a physical failure in the sensor that monitors the heat of the exhaust gases. The most common reason is that the sensor's internal wiring has degraded or failed entirely, leading to an incorrect electrical signal that forces the boiler to shut down to prevent overheating.
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 b0 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann b0 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
- Viessmann Vitodens 050-W BPJD manual (PDF)
- Viessmann Vitodens 100-W WB1B manual (PDF)
- Viessmann Vitodens 111-W manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026