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Home >> Geo >> 1995 >> Metro Base, 2D Hatchback >> Repair and Diagnosis (Single Page) >> Engine Performance >> Theory and Operation >> Engine Controls - Theory & Operation - 1.3L 4-CYL >> Computerized Engine Controls >> Input Devices >> Vehicle Speed Sensor (VSS)

Vehicle Speed Sensor (VSS)

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