Throttle Positioner System: Operation: Corolla
The throttle positioner system is vacuum controlled. When the throttle is open and vacuum at the TP port is low, the positioner moves to the set position. When the throttle is released, as during deceleration, the positioner keeps it from closing completely until vacuum bleeds through the VTV. High vacuum present at TP port will then pull the positioner back and allow the throttle to close completely.