Failure of Variable Assist Power Steering at low speeds on 2008 Saturn Vue

I just purchased a used Saturn Vue XR and the Power Steering pump was replaced when the power steering failed at low speeds. This seemed to resolve the issue for about an hour. When braking, or starting from a stop the steering wheel is nearly impossible to turn in any direction. If I give it power via the accelerator it becomes easier to steer. What could be causing this if the pump is good?

Asked by for the 2008 Saturn Vue