BoilerFaultCodesWhat the manual says
Manufacturer manualControl mode - Communication fault Vitocom 100 (KMBUS)
What causes this fault?
This fault occurs when the boiler's main control board loses its electronic handshake with the internet or remote control module. It is usually caused by a loose connection plug or a hardware failure within the communication module itself, preventing your thermostat or app from talking to the boiler. In some cases, a brief power surge can disrupt this data link, requiring the module to be checked or reset.
DIY fix possible
Check that your internet router is switched on and functioningEnsure the Vitocom communication module is plugged in and poweredReset your boiler by turning it off and on again to re-establish the link
Avoid the next call-out bill
A cover plan would handle faults like Cd: no call-out fees, no surprise bills.
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Related fault codes
All 75 fault codes on the Vitodens 333 WS3A
Seeing a different code? Every code this model can display, in one place.