Also, if you have access to a frequency counter (either a standalone one or built into a multimeter) the vehicle speed sensor outputs 8000 pulses per mile. So at 50MPH it should read about 111Hz, if my math is correct.
50 * 8000 / 3600 = 111
Or
(fHz * 3600) / 8000 = sMPH
Where fHz is the frequency in Hz
and sMPH is the vehicle speed in MPH.
Even easier:
fHz * 2.22 = sMPH
Brian
