2020 Subaru WRX BaseFACTORY OEM SERVICE PROCEDURE

Camshaft Position Sensor (Method With Oscilloscope)

  1. Disconnect the ground terminal from battery sensor. Refer to NOTE>NOTE>BATTERY .
  2. Prepare an oscilloscope.
  3. Remove the engine control module (ECM). Refer to FUEL INJECTION (FUEL SYSTEMS) (W/O STI)>ENGINE CONTROL MODULE (ECM)>REMOVAL .
  4. Install the ST between the ECM and bulkhead harness and the engine wiring harness. Refer to ENGINE (DIAGNOSTICS) (W/O STI)>GENERAL DESCRIPTION>CAUTION .
    ST 18460AA030 CHECK BOARD
  5. Connect the ground terminal to battery sensor. Refer to NOTE>NOTE>BATTERY .
  6. Connect the probe to ST.
    G12444184Courtesy of SUBARU OF AMERICA, INC.
    Camshaft position sensor Terminal No. Probe
    Intake RH (E158) No. 20 +
    LH (E158) No. 21 +
    Exhaust RH (E158) No. 32 +
    LH (E158) No. 33 +
    RH and LH (E159) No. 10 -
  7. Start the engine and let it idle.
  8. Check the waveforms and voltage.
    NOTE: For waveform and voltage, refer to "Engine Control Module (ECM) I/O Signal". Refer to ENGINE (DIAGNOSTICS) (W/O STI)>ENGINE CONTROL MODULE (ECM) I/O SIGNAL .
  9. After inspection, install the related parts in the reverse order of removal.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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