Vehicle Speed and Distance Sensor-PCM Input

Fig. 8 Vehicle Speed Sensor Location-Typical:

VEHICLE SPEED AND DISTANCE SENSOR-PCM INPUT
The vehicle speed sensor is located on the speedometer pinion gear adapter (Fig. 8). The pinion gear adapter is located on the extension housing of the transfer case (drivers side). The sensor input is used by the Powertrain Control Module (PCM) to determine vehicle speed and distance traveled.

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.

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

Under deceleration conditions, the PCM adjusts the Idle Air Control (IAC) motor to maintain a desired MAP value. Under idle conditions, the PCM adjusts the IAC motor to maintain a desired engine speed.

CIRCUIT OPERATION
Circuit K6 supplies 5 Volts from the Powertrain Control Module (PCM) to the vehicle speed sensor. The K6 circuit connects to cavity B31 of the PCM.

Circuit G7 from the vehicle speed sensor provides an input signal to the PCM. The G7 circuit connects to cavity B27 of the PCM.

The PCM provides a ground for the vehicle speed sensor signal (circuit G7) through circuit K167. Circuit K167 connects to cavity A4 of the PCM.