The first stage that I had to do was work out how everything would fit together, where it would position best and follow the instructions for positioning the sensors. The kit itself was straight forward, it had 4 sensors with removable connectors, then several lengths of labelled cable (labelled A, B, C, D), a control box and small display. This is the control box and display that came with mine:
So, the thing that I thought would be best, would be to get all of the sensors and somehow attach them to the bumper, see if my calculations looked correct before I drilled my precious bumper (That bit REALLY scared me, as if that went wrong, its time to buy a new bumper!). So I tried a few different ways of temporarily fastening them, all failing because the back of the sensor had the cable fitted directly to it, no flushed mount cables or anything like that, so trying to attach it to a flat surface didn't really work. So, I then realised, the box that they came in had a plastic packaging tray, that if I cut up would work perfectly! Who said I didn't have good ideas sometimes ;-) So I fasioned that up and attached them with simple double-sided tape:
As you can see, the sensor dangling, and my make-shift mounting bracket. Looks classy!
So, I fitted them all on like that to see what positions, etc looked ok, and it didn't look too bad:
So a quick power-on showed the sensors all working, and the distance was showing up with 0.5 which I assumed was correct as I was reversed up against my garage. One thing I did notice however is that the sensors slightly pointed downwards, which may be a problem, so something to watch for otherwise I'd guess it would generate erroneous results.
I then thought that the testing had worked fine, so time to go for broke, and work out how to remove the bumper. As this is a big American car, generally its put together pretty easily, and I'm glad to say the bumper was quite simple to remove. Firstly you open the boot, then inside the wheel-arch you'll find 3 screws, this poses a problem, the screws are around 2inches away from the rear tyre, so no screwdriver I had would fit. But improvisation, this is where a small screwdriver attachment (the ones you put on drills to electric drivers) and a spanner, grab the attachment in the jaws and you can manage to slowly remove the screws. Once all three are out, move round to the inside of the boot, and you'll see a single screw diagnoally down from the light cluster. Move to the opposite side and repeat this process. That's all the main screws undone, now for the REALLY tricky ones, underneath there are 4 push-clips. I took a picture of these as they are probably the most challenging part of the operation!
Here I've removed the bumper, and you can see the slightly odd site I found behind it, this is a polystyrene cover over the metal girder that is the main bumper, not what I'd expected but this looked like it might prove a problem. The problem was that the polystyrene would be right in the way of the sensors. Since I couldn't think of a solution I bashed on, and thought that I'd be able to solve this later.
I then used the drill-bit that was supplied to drill the holes where I'd measured. This worked fine, so I then fitted the sensors in, and they looked pretty neat!
Once off you could see the rubber bung under the carpet in the boot, so remove the bung and feed the cables in using a small hole to secure it all. It was easier to drop the spare tyre at this point so it was easier to work underneath the car. Feed the cables in, and I decided to hide the small control box inside the jack storage.
Next problem, wiring harness for the reverse lights (This unit is easier to wire straight into the reverse lights, so that it turns on when the car was in reverse), now myself and several others owners had talked about towing and where the tow-cables went, etc. It seems this is a bit of a mystery on these cars, as they all have slightly different wiring methods, where the wiring bundles are, etc. Now whilst taking panels apart, I took apart the plastic trim on the left hand side of the car and found the main wiring loom, and also a large plastic box with most of cables feeding into. Since I couldn't prise the plastic trim any further (I'd removed both screws and popped several clips, but I suspect because of the electric/motor power boot open/close that I wouldn't be able to fully remove the plastic panel without taking apart more mechanics of the car). I gave up trying to look into the electronics box, maybe something to do at a future date as I'm now curious what this is and what it does. So I went for plan B, basically testing which cables carried voltage when the reverse lights were on, and just splice into those. Easily done with the multi-meter, and wired in. Interestingly I also did a web search on wiring tow-bar wiring for these cars, and most of them do a similar job, they simply provide a connector socket and plug, you unplug the lights cluster from the rear lights, plug the cable into the tow-bar loom, and then plug back into the lights (so a man-in-the-middle type wiring). Power to the lights worked fine, and the unit came on no problem at all.
Re-attaching the bumper was simple, just hold the bumper back in place, clip around on the left and right inside the wheel-arch then re-attach the screws. Simple!
The whole job took around 3 hours with breaks, so not a particularly tricky one, and hopefully a few tips here will help out if you need to remove the bumper or do anything at the back of your Grand Voyager