Vehicle Speed Sensor: Description and Operation

PURPOSE/OPERATION
The vehicle-speed sensor is incorporated within the speedometer; it converts vehicle-speed data to pulse signals and inputs those signals to the engine control module. The engine control module, based upon those signals, regulates the idle-speed motor, etc.
The vehicle-speed sensor, by intermitting by the lead switch the flow (to ground) of the approximately 5 Volt voltage applied from the engine control module, produces vehicle-speed signals.