Rear Oxygen Sensor: Removal

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

Fig 1: Disconnecting Ground Cable From Battery
Courtesy of SUBARU OF AMERICA, INC.
Lift up the vehicle.
Disconnect the connector from the rear oxygen sensor, and remove the clip (A) holding the rear oxygen sensor harness.

Fig 2: Identifying Clip
Courtesy of SUBARU OF AMERICA, INC.
Apply spray-type lubricant or equivalent to the threaded portion of rear oxygen sensor, and leave it for one minute or more.
Remove the rear oxygen sensor.
CAUTION: When removing the rear oxygen sensor, wait until exhaust pipe cools, otherwise it will damage the exhaust pipe.

Fig 3: Identifying Rear Oxygen Sensor
Courtesy of SUBARU OF AMERICA, INC.