Vehicle speed output

ABS HU/CM terminal: Q (+) - AA(-)
Oscilloscope setting: 2 V/DIV (Y), 25 ms/DIV (X)
Vehicle condition: Driving 25 km/h [15.5 mph]
NOTE:
- As Vehicle speed increases, period of wave shortens.
  
  Fig 1: Inspecting Vehicle Speed Output Using Oscilloscope
  Courtesy of MAZDA MOTORS CORP.