The knock sensor(s) is/are mounted in the engine valley between the cylinder heads. 2007 and earlier models have one sensor, while 2009 and later models have two. To access them, remove the upper intake manifold. Next, disconnect the knock sensor electrical connector. Following this, remove the sensor mounting bolt, then remove the sensor. Installation is the reverse of removal. Ensure to tighten the mounting bolt to 16 ft-lbs.