To replace the knock sensor, begin by releasing the pressure from the fuel system and disconnecting the negative battery terminal. For four-cylinder models, remove the intake manifold and disconnect the electrical connector to access the knock sensor. Slide the sensor off the mounting stud, install the new sensor, and tighten the nut to 15 ft-lbs. As for the V6 engine models, remove the lower intake manifold. After that, unplug the knock sensor harness connector. Remove the sensors, clean the mounting surface, and install the new sensors. Tighten the bolts securely. In both cases, reinstall any parts that were removed and refill the cooling system.