Front Oxygen (A/F) Sensor: Removal

Disconnect the ground terminal from battery sensor. Ref. to BATTERY
Lift up the vehicle.
Remove the under cover. Ref. to REMOVAL , Front Under Cover.
Disconnect the front oxygen (A/F) sensor connector, and remove the clip holding the front oxygen (A/F) sensor harness.

Fig 1: Identifying Front And Rear Oxygen Sensor Connectors And Clip
Courtesy of SUBARU OF AMERICA, INC.
Lower the vehicle.
Apply spray-type lubricant (004301003) or equivalent to the threaded portion of front oxygen (A/F) sensor, and leave it for one minute or more.
Remove the front oxygen (A/F) sensor.

CAUTION: When removing the front oxygen (A/F) sensor, wait until exhaust pipe cools, otherwise it will damage the exhaust pipe.

Fig 2: Identifying Front Oxygen (A/F) Sensor

Courtesy of SUBARU OF AMERICA, INC.