Knock Sensor
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
The Knock Sensor (KS) is a tuned accelerometer located on the engine, which converts engine vibration to an electrical signal. PCM uses this signal to determine the presence of engine knock and retards spark timing accordingly.