Vehicle Speed Sensor

Vehicle speed sensor is a reed switch mounted on rear of instrument cluster and rotates with the speedometer cable. With each rotation of speedometer cable, vehicle speed sensor turns on and off 4 times and delivers an input signal to Engine Control Module (ECM). The ECM determines vehicle speed by using the input signal and may use input signal for controlling fuel injection system, ignition timing (spark advance), idle speed control system (some models), A/C cut-control system (some models).