Vehicle Speed Sensor Operation

OPERATION
The Vehicle Speed Sensor (VSS) is a pulse generator mounted to an adapter near the transmission output shaft. The sensor is driven through the adapter by a speedometer pinion gear. The VSS pulse signal to the speedometer/odometer is monitored by the PCM speed control circuitry to determine vehicle speed and to maintain speed control set speed. Refer to the appropriate Powertrain Diagnostic Procedures for diagnosis and testing of this component in Powertrain Management/Computers and Control Systems.

The speed sensor generates 8 pulses per sensor revolution. These signals, in conjunction with a closed throttle signal from the throttle position sensor (auto. trans. only), indicate a closed throttle deceleration to the JTEC. When the vehicle is stopped at idle, a closed throttle signal is received by the JTEC (but a speed sensor signal is not received).

In addition to determining distance and vehicle speed, the output from the sensor is used to help control:

- Speed control operation
- Transmission overdrive operation
- Transmission torque converter electrical operation