Envoy 2WD V6-4.3L VIN W (1998)
Transmission Speed Sensor: Description and Operation
VEHICLE SPEED SENSOR
IMPORTANT: The sensor resistance is model dependent and varies with speed from a minimum of 0.5 volts AC at 100 RPM to more than 100 volts
AC at 8000 RPM.
DESCRIPTION
The vehicle speed sensor (or transmission output speed sensor) controls shift points and calculates the Torque Converter Clutch (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. DTC P0502 will set if a fault exists in the vehicle speed sensor circuit 40 PPR line.
