On a much older bike with a much more "simple" BMS, fault codes and electronics.
Speedometer not working.
GS911 told : "Speed implausibe" To me that meant a "ABS" fault
Switched sensor and checked whatever. Never got it to work.
A few months later I had to remove the instument kluster so removed the (ziptied from factory) connectors.
After replacing the cluster the speedometer worked. (have worked for 2 years now)
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I am not at all sure of how it works on a 2007 R1200GS but think there are 2 separate wires, one feeding the speedo and one the trip. A third connecton used to check if the saved milage correspond to what is stored in the BMS.
The Kombi is a "clever" instrument unit and check if its installed on the right bike.
Haakon