The code often indicates that the flow rate on the primary side is too low .
If air is trapped in the system, it can cause flow errors. Use a radiator key to bleed any air until water starts to flow steadily. Perform a System Reset: For Vitodens/Vitocal models: viessmann d6 error
✅ If the boiler fires up and runs normally, the error was a one-off. ❌ If D6 returns immediately or after a few minutes, continue. The code often indicates that the flow rate
Sometimes a temporary electronic glitch causes the error. Try a simple reset by following the instructions in your manual or using the Viessmann Fault Code Checker for your specific model. viessmann d6 error