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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 27 (ANALOG INSTRUMENT PANELS)OPERATIONGAUGESVEHICLE SPEED SENSOR
1999 GMC Forward Control 5.7 R, Automatic

Vehicle Speed Sensor

1999 GMC Forward Control 5.7 R, AutomaticSECTION Vehicle Speed Sensor
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2001 GMC Savana Special, 2001 GMC Savana Camper Special, 2001 GMC Savana, 2001 Chevrolet RV Cutaway, and 2001 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

The Vehicle Speed Sensor (VSS) assembly provides vehicle speed information to PCM. VSS assembly is a permanent magnet (PM) generator. PM generator produces a pulsing AC voltage as rotor teeth on transmission output shaft pass through the sensor's magnetic field. AC voltage level and the number of pulses increase as speed of vehicle increases. Output voltage varies with speed from a minimum of 0.5 volt at 100 RPM to more than 100 volts at 8000 RPM. PCM converts the pulsing voltage to vehicle speed. PCM uses the vehicle speed signal to determine shift timing and TCC scheduling.

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