Vehicle Speed Sensor (VSS)

Vehicle speed sensor consists of a reed switch and magnet located in speedometer head. As magnet rotates with speedometer cable, magnet causes reed switch to turn on and off. Switching action increases or decreases in proportion with vehicle speed. Switch ECM supplies and monitors a voltage signal to speed sensor. ECM uses this signal to help determine control of Idle Air Control (IAC) valve and shift-up indicator light (Swift SOHC).