DTC P0502: VSS Circuit - Low Input (M/T Without Abs): Description
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.
Vehicles equipped with M/T without anti-lock brakes receive vehicle speed from a right front wheel speed sensor. Right front wheel speed sensor produces an AC voltage of different amplitude and frequency depending on velocity of right front wheel. Sensor produces a readable AC voltage signal when vehicle speed is more than 3 MPH. Speed signal is sent to a wheel speed signal conditioner module, which converts AC voltage of sensor to a square wave. Square wave is produced by condition module grounding White wire from PCM, which is pulled up to 5 volts through a resistor on PCM. DTC sets when PCM does not detect a square wave vehicle speed signal for a certain length of time.