Vehicle Speed Sensor (VSS)

Important: The sensor resistance should be 1260-1540 ohms when measured at 20° C (68° F). Output voltage varies with speed from a minimum of 0.5 volts AC at 100 RPM to more than 100 Volts AC at 8000 RPM.

The vehicle speed sensor (or transmission output speed sensor) controls shift points and calculates the TCC slip.

The speed sensor contains a coil that gives off a continuous magnetic field. A rotor rotates past the sensor and the rotor teeth break the magnetic field. Each break in the field sends a pulse to the VSSB (Vehicle Speed Sensor Buffer). The VSSB sends two signals to the PCM. The first is a 2002 pulse per mile (PPM) signal that is used by the engine. The second is the transmission/transfer case 40 pulse per revolution (PPR) signal that is used in order to control the transmission.

In two wheel drive (2WD) applications, the vehicle speed sensor is located on the transmission extension housing. Trans Output Speed = Transfer Case Speed.

Codes 024 or 072 will set if a fault exists in the vehicle speed sensor circuit 40 PPR line.