My car apparently has power 'assisted' steering which is 'sensed' by the speed of the car. Works fine on the hwy at 40mph+, but no power steering available at low mph, u-turns, parking, etc.. I'm told that there is a 'valve' (Solenoid Valve?) inside the power steering gear box that is the mostly likely culprit. Fluid level is fine and there are no leaks.