Your boiler has lost its connection to the remote control or internet monitoring system, so you may not be able to adjust settings via your app or external thermostat.

Communication error, Vitocom 100 (KM BUS)

What causes this fault?

This fault occurs when the boiler's main control board loses its digital handshake with the communication module responsible for internet connectivity. It is usually caused by a loose connection cable, a temporary glitch in the module's hardware, or a complete failure of the Vitocom unit itself. While the boiler will continue to provide heat based on its last known settings, it can no longer receive new instructions from your smartphone or remote thermostat.