Rear Oxygen Sensor: Removal

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

Fig 1: Disconnecting Ground Cable From Battery
Courtesy of SUBARU OF AMERICA, INC.
Remove the clip fastening the harness and disconnect the rear oxygen sensor connector.

Fig 2: Identifying Front Oxygen And Rear Oxygen Sensor Connector
Courtesy of SUBARU OF AMERICA, INC.
Lift-up the vehicle.
Remove the under cover.
Apply spray-type lubricant 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, because it can damage the exhaust pipe.

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