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Home >> Chevrolet >> 1998 >> Prizm Base, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> Theory and Operation >> Engine Controls - Theory & Operation 1.8L >> Computerized Engine Controls >> Input Devices >> Vehicle Speed Sensor (VSS) (Transmission Mounted)

Vehicle Speed Sensor (VSS) (Transmission Mounted)

VSS consists of a reed switch built into speedometer head. PCM applies 5 volts to VSS. As speedometer cable rotates, reed switch closes circuit to ground 4 times per revolution. As vehicle speed increases, frequency of ground impulses increases. This pulse is sent to PCM and is used to calculate vehicle speed.