BoilerFaultCodesViessmann 19 Fault Code
The Viessmann 19 fault code means: your boiler has lost its wireless connection to the sensor that measures the temperature outside, which may cause your heating to be less efficient.. It appears on 2 Viessmann models in our database.
Technical description: Communication error with wireless outside temperature sensor
DIY fix possible
Check the batteries in your outdoor wireless temperature sensor and replace them if necessary.Ensure there are no new large metal objects or electronic devices blocking the signal between the sensor and the boiler.Reset the boiler to see if it automatically re-establishes the wireless link.
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Viessmann models that show the 19 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 19 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 7 July 2026