Primary Speed Sensor: Inspection

Remove the instrument panel lower cover. Refer to REMOVAL .
Set the probe of oscilloscope to TCM harness connector.
Connector & terminal

(B54) No. 6 (+) - No. 1 (-):

Fig 1: TCM Harness Connector Terminal Identification
Courtesy of SUBARU OF AMERICA, INC.
Start and warm up the engine.
Lift up the vehicle.
CAUTION: Lift up the vehicle until the tire bottom is 0.3 m (0.98 ft) or more above the ground.
Shift the select lever to "D" range.
Check the waveform of primary speed sensor with engine idling running.

Fig 2: Primary Speed Sensor Output Voltage Waveform
Courtesy of SUBARU OF AMERICA, INC.