Eldorado V8-300 4.9L (1991)
Vehicle Speed Sensor: Description and Operation
Vehicle Speed Sensor
The Vehicle Speed Sensor (VSS) is a pulse generator which is mounted in the transaxle. A toothed reluctance ring rotates near a magnetic pick up,
producing a voltage signal that is proportional to the vehicle speed. The speed sensor produces a weak signal. A vehicle speed sensor buffer amplifier is
placed between the speed sensor and the PCM/ECM to amplify the speed signal. The buffer amplifier decodes the signal from the speed sensor to a
digital signal, and sends it to the PCM/ECM. The PCM/ECM uses this signal for the logic required to operate the fuel economy data panel, the integral
cruise control, the idle speed control system, Viscous Converter Clutch (VCC), and to modify fuel delivery under certain vehicle conditions. A speed
sensor or circuit which is not functioning properly will set a code E024. An intermittent problem can also set code E075.
