Front Oxygen (A/F) Sensor: Removal

Set the vehicle on a lift.
Remove the collector cover.
Disconnect the ground cable from battery.

Fig 1: Disconnecting Ground Cable From Battery
Courtesy of SUBARU OF AMERICA, INC.
Disconnect the connector from the front oxygen (A/F) sensor, and remove the clip (A) holding the return hose and the front oxygen (A/F) sensor harness.

Fig 2: Identifying Front Oxygen (A/F) Sensor And Clip
Courtesy of SUBARU OF AMERICA, INC.
Remove the clip (A) and (B) holding the front oxygen (A/F) sensor harness.

Fig 3: Identifying Clip And Front Oxygen (A/F) Sensor Harness
Courtesy of SUBARU OF AMERICA, INC.
Lift up the vehicle
Remove the under cover.
Apply spray-type lubricant 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 oxygen (A/F) sensor, wait until exhaust pipe cools, otherwise it will damage the exhaust pipe.

Fig 4: Identifying Front Oxygen (A/F) Sensor

Courtesy of SUBARU OF AMERICA, INC.