Vehicle Speed Sensor: Description and Operation

PURPOSE
The Vehicle Speed Sensor (VSS), located rear of the transmission on the differential, is used by the Programmed Fuel Injection Electronic Control Module (PGM-FI ECM) to determine vehicle speed and by the speedometer to drive the trip odometer/mileage odometer stepper motors and the speedometer driver to indicate vehicle speed.

OPERATION
The speed sensor pulses the signal wire, switching its connection to ground on and off. The number of pulses increasing with vehicle speed. This signal is used to operate the stepper motors for the trip/mileage odometer, and the speedometer driver to indicate vehicle speed. This same signal is used by the PGM-FI ECM to determine vehicle speed for PGM-FI operation.