2020 Subaru WRX BaseFACTORY OEM SERVICE PROCEDURE

Front Oxygen (A/F) Sensor: Installation

CAUTION: If lubricant is spilt over the exhaust pipe, wipe it off 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)

  3. Secure the front oxygen (A/F) sensor harness to the water pump cover using clip (B), and connect the front oxygen (A/F) sensor connector (A) to the engine wiring harness.
    G10266244Courtesy of SUBARU OF AMERICA, INC.
  4. Install the under cover. Refer to EXTERIOR/INTERIOR TRIM>FRONT UNDER COVER>INSTALLATION .
  5. Lower the vehicle.
  6. Install the radiator main fan & fan motor assembly. Refer to COOLING(W/O STI)>RADIATOR MAIN FAN AND FAN MOTOR>INSTALLATION .
  7. Connect the ground terminal to battery sensor. Refer to NOTE>NOTE>BATTERY .
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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.