Circuit Description

Vehicle speed sensor circuit consists of a magnetic, induction-type sensor, vehicle speed sensor buffer/module and wiring. Gear teeth pressed on output shaft induce an alternating current in sensor. Signal is transmitted to buffer. Buffer compensates for various axle ratios and converts signal into a square wave for use by speedometer, cruise control, anti-lock brakes and PCM. Buffer sends 2 different signals to PCM.

DTC will set when the following conditions are present:

Vehicle speed is greater than 20 MPH.
Four wheel low is not selected.
VSS buffer calculated speed is less than half of transmission calculated speed.
Conditions are met for 2 seconds.

VSS buffer calculated speed is greater than transmission calculated speed by 20 MPH.