I have a 2007 Saturn Relay van with the Ultrasonic Parking Assist (rear sensors). The system seems to have quit working, as there are no alarms now and the lights inside near the lift gate do not come on either. What might have happened to cause this system to quit working? The overhead console switch to disable/enable the system is on. Is there supposed to be any voltage going to these sensors? I have heard about a control module somewhere, does anyone know where it is or how to check it?