Vehicle Speed 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.
Vehicle Speed Sensor (VSS) is a variable reluctance or Hall Effect type sensor that generates a waveform with a frequency that is proportional to vehicle speed. When vehicle is moving slowly, sensor produces a low frequency signal. As vehicle speed increases, sensor produces a higher frequency signal. PCM uses this signal to control fuel injection, ignition timing and transaxle/transmission shift and Torque Converter Clutch (TCC) scheduling.