Circuit/System Description

The engine control module (ECM) creates the vehicle speed output signal by pulsing the circuit to ground at a rate of 4 KPPM. The VSS input is pulled high to B+ in the instrument panel cluster (IPC). The IPC converts the 4 KPPM vehicle speed signal to a speedometer position to indicate the vehicle speed. The ECM monitors the voltage at the vehicle speed signal circuit to determine when the voltage is out of the normal operating range.