Primary Speed Sensor: Inspection

Set the probe of oscilloscope to TCM harness connector.
Connector & terminal

(B54) No. 6 (+) - No. 14 (-):

Fig 1: Setting Probe Of Oscilloscope To TCM Harness Connector
Courtesy of SUBARU OF AMERICA, INC.
Start and warm up the engine.
Check the waveform of primary speed sensor with engine idling.
NOTE: The waveform cycle changes as the speed changes.

Fig 2: Primary Speed Sensor Waveform (With Engine Idling)
Courtesy of SUBARU OF AMERICA, INC.