The knock control system is also intended for leading spark knock during the period of heavy detonation to give the engine optimum spark advance for driveability. The knock sensor senses the vibration in the engine that is due to knock and gives a voltage output proportional to the degree of knock. This voltage signal is felt by the PCM that slows down the ignition timing until the detonation is over. The knock sensor is mounted at the back of the EM, toward the rear of the car, right below the cylinder head. First, to remove the sensor, the cable of the negative terminal of the battery should be disconnected, the cooling system should be emptied and the intake manifold should be unbolted. Then, unscrew the knock sensor that is bolted to the side of the block beneath the intake manifold and unclip the electrical connector. If using the old sensor, was the threads with thread sealant as all new sensors come threaded; do not overdo the sealant else the sensor will not work as required. Securely bolt in the knock sensor, without over tightening, reconnect the electrical connector, replace the cooling system fluids, and confirm that there are no leaks.