Wave Profile Inspection

Remove the PCM. (See PCM REMOVAL/INSTALLATION .)
Connect WDS or equivalent to DLC-2 connector.
Connect oscilloscope test leads to the following PCM connector terminals.
- (+) lead: PCM terminal 3V
- (-) lead: PCM terminal 4A
Start the engine.
Monitor RPM PID.

Fig 1: Identifying PCM Connector Terminal
Courtesy of MAZDA MOTORS CORP.
Inspect wave profile when idling engine.
- If wave profile or voltage are out of specifications, carry out the "Circuit Open/Short Inspection".
  - PCM terminal: 3V(+) <--> 4A(-)
  - Oscilloscope setting: 2.0V/DIV(Y), 20ms/DIV(X), DC range
  - Vehicle condition: Idling
Fig 2: Identifying Waveform Graph
Courtesy of MAZDA MOTORS CORP.