Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor (VSS)

For F-Series and Excursion, the VSS signal is generated by Generic Electronic Module (GEM). The GEM generates VSS from a speed sensor on the rear axle.


On vehicles equipped with 4-Wheel Anti-lock Brake Systems (4WABS), the vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input. Vehicles equipped with Rear Anti-lock Brakes (RABS) generate a vehicle speed signal from the rear axle speed sensor. The Generic Electronic Module (GEM) receives this signal (VSS_GEM) for internal use and then distributes it to the appropriate other users (i.e., the Powertrain Control Module [PCM], speed control module, and speedometer). On motorhome, the VSS signal is transmitted to the instrument cluster from the powertrain control module (PCM) through hardwired circuitry.