BoilerFaultCodesViessmann E1 Fault Code
The Viessmann E1 fault code means: your boiler is struggling to accurately measure its own flame quality during a self-check, which prevents it from firing up safely.. It appears on 2 Viessmann models in our database.
Technical description: Ionisation current too high during calibration
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 E1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann E1 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