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).