That is not what is supposed to do. Something behind you from the begining when you back up will not trigger the BCI, You will see it through your backup camera, unless you are not looking. It will kick in if someone or something comes out in cross traffic when you back up. So your test is invalid. When you back up, ask someone to throw a big card box in your way, see if it works. PLus, it has a speed limit, if you back up too fast, it will be disabled.