How to use/activate/start the audi parking system in my Q7?

The beep noise that your supposed to hear when you're reversing and there is an object close to you doesn't work for me...it used to work, but now it just does a loud beep when i change the gear into reverse and after that something can go behind the truck without the beep noise happening. How do I make it work?How to use/activate/start the audi parking system in my Q7?The one loud beep and then no activity means the system is malfunctioning. Make sure the sensors are not too dirty or otherwise obstructed, and if that doesn't help you need to get it looked at.