Vehicle Speed Sensor (VSS)
VSS is located on transaxle. See Fig 1 . VSS generates 4 pulse signals for each rotation of speedometer driven gear. ECM will interpret VSS input along with TP sensor closed throttle input.
These inputs allow ECM to differentiate between closed throttle deceleration and closed throttle idle (vehicle stopped) conditions. During deceleration, ECM controls IAC motor to maintain desired manifold pressure value. During idle (vehicle stopped), ECM controls IAC motor to maintain desired idle speed.