2019 Subaru WRX STI Series.GrayFACTORY OEM SERVICE PROCEDURE

Front Oxygen (A/F) Sensor: Installation

CAUTION: If lubricant is spilt onto the exhaust pipe, wipe it off completely with cloth to avoid emission of smoke or causing a fire.
  1. Before installing front oxygen (A/F) sensor, apply anti-seize compound only to the threaded portion of front oxygen (A/F) sensor to make the next removal easier.
    CAUTION: Never apply anti-seize compound to the protector of front oxygen (A/F) sensor.

    Anti-seize compound: 

    NEVER-SEEZ NSN, JET LUBE SS-30 or equivalent

  2. Install the front oxygen (A/F) sensor.

    Tightening torque: 

    30 N.m (3.1 kgf-m, 22.1 ft-lb)

    G08538815Courtesy of SUBARU OF AMERICA, INC.
  3. Install the under cover. Refer to EXTERIOR/INTERIOR TRIM>FRONT UNDER COVER>INSTALLATION .
  4. Lower the vehicle.
  5. Secure the front oxygen (A/F) sensor harness to the engine harness stay using the clips (A).
    G08538814Courtesy of SUBARU OF AMERICA, INC.
  6. Connect the connector to the front oxygen (A/F) sensor, and secure the return hose and front oxygen (A/F) sensor harness using the clip (A).
    G12437348Courtesy of SUBARU OF AMERICA, INC.
  7. Connect the battery ground terminal.
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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.