Did anyone who has " Park Assist" (the 4 sonar backup sensors in the rear bumper) get any operating instructions? There is nothing I can find in the owner's manual. On the dash is a pushbutton marked "Park Assist" which the salesman told me turned it off, I've no idea why I should turn it off! Further there seems to be no indication whether it is on or off. If I accidentally touch the button with my knee I assume I won't know it's off until I hit the wall when I back into a parking spot? If this is the case it doesn't seem to be anything I can rely on.