That sensor goes to the diagnostic connector only. It's supposed to indicate TDC (top dead center). The signal itself is measured on pin 8 relative to pin 10, and the cable shield runs to pin 9. None of these signals go anywhere else- they are completely independent of everything else in the car. It might be useful to trigger a piece of diagnostic equipment if other signals are unreliable. I have a 1986 535i I was wondering what does the crank sensor in the front of the engine do. What is it used for?