Front Wheel Speed Sensor: Inspection

Remove the bulkhead harness connector from TCM. <Ref. to REMOVAL , Transmission Control Module (TCM).>
Set the ST between the TCM and bulkhead harness.
ST 18460AA040 CHECK BOARD
Set the probe of oscilloscope to the check board connector.
Terminals:

No. 12 (+) - No. 26 (-)

Fig 1: Identifying Check Board Connector Oscilloscope Positive And Negative Probes
Courtesy of SUBARU OF AMERICA, INC.
Lift up the vehicle and raise the vehicle speed up to 20 km/h (12 MPH).
Check the waveform of front wheel speed sensor when vehicle speed is at 20 km/h (12 MPH).
NOTE: The waveform cycle changes as the speed changes.

Fig 2: Front Wheel Speed Sensor Waveform
Courtesy of SUBARU OF AMERICA, INC.