Have a look at how the export reverse parking aid sensors (# KKJ103010) are installed:
The complete OEM Reverse Parking Aid kit:
You must be registered for see images
The kit includes 4 sensors
If you have an export tire carrier you will need to mount 2 of the sensors on the carrier
You must be registered for see images
You must be registered for see images
and run the wires through the rear cargo door.
Notice the blue wire running from the gate, to the serpentine plastic hose and to the left quarter panel.
You must be registered for see images
Lift the cargo area carpet from the left corner an drill through the small plate to run the wires from the bumper to the cabin.
Drilling trough is quite easy as the plate is very thin.
You do not need to remove the black cargo hook.
You must be registered for see images
Drilled wired and taped
You must be registered for see images
View under the jeep
You must be registered for see images
You will need to zip-tie them on a couple of spots, so as not to hand down the bumper.
Hope this covers your question.