Viessmann D6 Error May 2026

Viessmann D6 error primarily indicates a fault reported by an external device

communication problem between the boiler’s main printed circuit board (PCB) and the user interface

The D6 error code indicates a (the control panel where you set the temperature and hot water). viessmann d6 error

Because the EA1 module is used to integrate external components, the "real" problem often lies outside the boiler itself: External Pump Failure: Viessmann D6 error primarily indicates a fault reported

If a power cable is run tightly parallel with the KM-BUS cable for a long distance, electrical noise can corrupt the data signal. Exact model and serial number

• Exact model and serial number.
• Error code (D6) and any other codes or lights.
• What you’ve already tried (reset, gas supply checks, condensate).

What Does the D6 Error Code Mean?

When the boiler tries to ignite, you should hear: