BoilerFaultCodesViessmann 02 Fault Code
The Viessmann 02 fault code means: your boiler has shut itself down as a safety precaution because it has detected an overheating issue within the system.. It appears on 4 Viessmann models in our database.
Technical description: Burner control switches to lockout
What causes the Viessmann 02 fault?
This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety sensor to cut the power to the burner. The most common reasons include a failing pump that isn't moving water away from the burner quickly enough, or a buildup of debris and sludge that is restricting flow through the heat exchanger.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after sitting idle all summer, which can cause internal pump components to seize.
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 02 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 02 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 manual (PDF)
- Viessmann Vitodens 111-W manual (PDF)
- Viessmann Vitopend 100 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026