BoilerFaultCodesViessmann 76:2 Fault Code
Also written as 762 — same fault.
The Viessmann 76:2 fault code means: your boiler is having trouble communicating with its internal control modules or multiple boiler system systems, which may stop it from operating correctly.. It appears on 5 Viessmann models in our database.
Technical description: With KM BUS/cascade communication module; automatic recognition
What causes the Viessmann 76:2 fault?
This fault occurs when the boiler's brain loses contact with the internal communication modules that coordinate its heating tasks. The most common reason is a loose or damaged wiring connection between internal components, or a electronic failure within the communication module itself. Essentially, the different parts of the boiler can no longer 'talk' to each other to confirm it is safe and ready to fire up.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Viessmann models that show the 76:2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 76:2 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026