July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

Engine Speed Signal

PCM terminal: 3O(+) <-> 4A(-)
Oscilloscope setting: 2.0 V/DIV (Y), 20 ms/DIV (X), DC range
Vehicle condition: Idling

Fig 1: Identifying Fuel Engine Speed Signal
Courtesy of MAZDA MOTORS CORP.