Vehicle Speed Sensor: Description and Operation

PURPOSE
The Vehicle speed sensor is a Reed switch type unit used by the ECM for fuel injector duration calculations, and for the Cruise Control to determine road speed.

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 air control motor, etc..

Pulses are produced in accordance with the vehicle speed, and vehicle-speed signals are input to systems (the MFI system, etc.) that regulate according to the vehicle speed.