Hi Chris
We have parking sensors fitted to our Sorento, they only work when you select reverse gear so if your van is attached when reversing they will go off. (because of the close proximity of the van to the car)
Can be a little anoying but if your'e quick at reversing it's not for long.
The wife loves them, she says as long as she doesn't hear a continuos tone she knows that she can't reverse into anything, must say me too.
Andy