Not sure if the G50 uses the same style of magnetic pickup as the 915, but if so you could check to make sure the sensor is properly in place and that the wires have not been damaged or pulled apart at the tunnel.
To test it's function you would probably need an oscilloscope, I'm not sure a volt meter would pick up these minute pulses.
Hopefully someone has experience with this. The sensor on the 915 is very easy to replace, can't comment on the G50.
