Originally Posted by chrish4ku
So Paulinator's 2008 S is still broke. Zero on the speedo, $330 spent at dealer troubleshooting, installing a new cable w/ sensor. Money wasted!
My head unit does the same thing on his bike (reads zero)
His head unit on my bike works.
It ain't the dash unit (check)
It ain't the sensor or cable (check)
I mean these bikes have NO ABS, and there are only 3 other wires as posted above and they seem to have 12V power via us checking with a voltmeter.
OK - fire up the suggestions..............
I'm looking at a wiring diagram for a 950 so assuming its the same still for the 08 990 the blue/yellow wire from the head unit is the positive/power for the speed sensor. I'm no electrical wiz but my guess would be that the sensor is creating an electromagnetic field with the power from this wire. The sensor wiring does not show a ground so I'm guessing one of the other two wires is the return for this electromagnet. The third wire would then be the one that actually sends the pulses generated in the sensor to the head unit. In short, if you are getting 12V between either of the three wires and a ground to the bike then something is amiss.
My first guess would be that there is a broken or shorted wire between the head unit connector and the speed sensor connector, its the only thing you haven't switched yet.