Vehicle Speed Sensor: Description and Operation

2 Wheel Drive (Manual Transmission)

VSS 2WD Manual Transmission:

2 Wheel Drive (Automatic Transmission)

VSS 2WD (A/TRANS.) VEHICLE SPEED SENSOR:

4 Wheel Drive or All Wheel Drive

VSS 4WD Or AWD:

PURPOSE
The Vehicle Speed Sensor (VSS) provides information to the control module for control of:
- Transmission Torque Converter8Clutch (TCC)
- Speedometer
- Odometer
- Cruise control
- ANTILOCK brake system.

CONSTRUCTION
The VSS is made up of:
- Permanent Magnet (PM) generator (coil), which is mounted on the transmission.
- Rotor (tooth), which is mounted on the output shaft in the transmission.
- VSS Buffer, which is mounted to the control module bracket.

OPERATION
The VSS is a Permanent Magnet (PM) generator that produces a pulsing Alternating Current (AC) voltage as each rotor tooth nears the coil. As the vehicle speed increases, the number of AC voltage pulses increase. The VSS buffer processes inputs from the VSS and outputs signal to the speedometer control module and cruise module. The VSS buffer takes the voltage pulses from the VSS and uses them to open and close four solid state output switches to ground at a rate proportional to vehicle speed. The VSS buffer is matched to the vehicle based on final drive ratio and tire size.