| on the M1000 the Tacho is combined with the Speedo and the the circuitboard is shared not only by both of them but also by the immobiliser that decodes the transponder in the key and sends another coded signal to the ECU.
so replacing the lot usually costs a bit.
The tacho signal should come straight from the ECU to the Clock connector via a green wire, all you can do with a test meter is check the continuity of the wire to check the pulses you ideally need an Oscilloscope or tap into the green wire with a known working tacho.
I had lots of telephone calls last monday about a similar problem
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