Two O2 sensors, same part number. The front one (bank 2) is near the oil filter. The rear one is more difficult to get to. I think that it is best accessed from under the car. Not sure. Anyway, an O2 socket is made to help get them out. Replacements come two ways: OEM style with the connector attached to the wire; and universal, where you need to cut off the connector and splice it to the new O2 wires. Wires are color coded.
