Disconnect the cable from the negative battery terminal. Raise the vehicle and place it securely on jackstands. On 4WD models, remove the front driveshaft. The OSS sensor is located on the upper left side of the transmission, at the rear. Note that on some later models, there are three speed sensors on the upper left side of the transmission. The OSS sensor is the rear one. Disconnect the electrical connector from the OSS sensor. Remove the OSS sensor retaining bolt. If you're planning to reuse the old OSS sensor, remove and discard the old 0-ring. Before installing the new 0-ring, lubricate it with petroleum jelly. Installation is the reverse of removal. Be sure to tighten the OSS sensor bolt securely.