Sometimes the error is a momentary glitch.
If a reset doesn't work, the issue is likely hardware-related. Because this involves opening the boiler casing and testing electrical circuits, a Gas Safe registered engineer (or equivalent local certified professional) should handle the following: viessmann d6 error
: Sometimes the Vitotronic "thinks" something is connected to DE1 when it isn't, or the settings for that input have been nudged out of place. Wiring Gremlins Sometimes the error is a momentary glitch
Look for flame detection problems
Before calling a technician, you can try these basic steps to see if the issue is a simple system hiccup: Check System Pressure: viessmann d6 error