Turbine Speed Sensor: Inspection

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

(B54) No. 20 (+) - No. 1 (-):

Fig 1: TCM Harness Connector Terminal Identification
Courtesy of SUBARU OF AMERICA, INC.
Start and warm up the engine.
Check the waveform and output voltage of the turbine speed sensor with engine idling.
NOTE: The waveform cycle changes as the speed changes.

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