Vehicle Speed Sensor-PCM Input

Fig. 17 Vehicle Speed Sensor -- Automatic Transmission:

Fig. 18 Vehicle Speed Sensor -- Manual Transmission:

PURPOSE
The sensor input is used by the PCM to determine vehicle speed and distance traveled.

OPERATION
The vehicle 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. Under deceleration conditions, the PCM adjusts the Idle Air Control (IAC) motor to maintain a desired MAP value.

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 idle conditions, the PCM adjusts the IAC motor to maintain a desired engine speed.

The vehicle speed sensor signal is also used to operate:
- Speedometer
- Speed control
- Daytime Running Lights (Canadian Vehicles only).

CIRCUIT OPERATION
Circuit K7 supplies 8 Volts from the Powertrain Control Module (PCM) to the vehicle speed sensor. The K7 circuit connects to cavity 44 of the PCM connector and cavity 3 of the vehicle speed sensor connector.

Circuit G7 from the vehicle speed sensor provides an input signal to the PCM. The G7 circuit connects to cavity 5 of the PCM and cavity 1 of the vehicle speed sensor.

The PCM provides a ground for the vehicle speed sensor signal (circuit G7) through circuit K4. Circuit K4 connects to cavity 51 of the PCM connector and cavity 2 of the vehicle speed sensor connector.