Bumper Removal & Reverse sensor fitting: GS300 Mk1

This workshop article relates to the removal of the fibreglass rear bumper section in order to accommodate wiring & fixing of reversing sensors as well as general maintenance etc. It does not relate to the removal of the actual bumper bar, which is the very substantial length of metal running the width of the car at the rear, designed & fitted to withstand accident impact.
The section relating to the sensors, although using an inexpensive alternative to certain other manufacturers, should be virtually the same in installation for most brands.
There are 6 bolts to remove on the outside, and 12 on the inside. You also need to remove a section of rear wheel-arch lining
(2x screws on each) to access one of the outside fixings.

10mm socket & wrench, and a posi-drive screwdiver are the basic tools req’d.

Remove all of the carpets etc. from the boot. These are held together with the push-fit type fixings.

There are 2 screws at the centre section, which are easy to see….

……..and one either side near to the wheel arch.
You then need to remove the small plastic rear section of the wheel arch liner to access the 2 final outside screws (one either side) ………..



Inside the boot, you now remove 4 screws at each side that secure the side sections of the bumper. Be careful not to drop any tools or nuts when doing the side where the CD changer is, as you will spend another 20 minutes unscrewing it all to get them back. (trust me on this one!)

The plastic scratch-strip on the boot ledge pops out (by hand).


and reveals the final 4 screws retaining the bumper…………..

Once the final 4 screws are undone, the bumper is ready to come off. First you need to pull out the screw lug from either side of the outer side section. I found a decent size screwdriver wrapped in a rag so as not to scratch any paint was suitable for this task.


The bumper is now free of any fixings and pulls off towards the rear.
There is only a few inches of play in the wires to the 2 number plate lights, so be careful not to let it drop. As I was only removing the bumper to accommodate my reversing sensors, I did not find it necessary to remove these. I was now able to drill & access the rear of it for threading wires etc.


22mm hole drilled either side for the sensors…………


The sensors I was using required a small degree of modification (due to the non-fancy, inexpensive nature of their manufacture), and had been previously taken apart, painted & lacquered, with the rest of the mounting discarded. A rubber grommet was similarly adapted to act as a new mounting.

The wires for each of them were then passed through each of the 2 number plate light grommets and into the boot.


Inside boot view of number plate lamp grommet/wiring.

Having fed the sensors & grommets through their holes, I then chose to fix and seal behind the bumper with filler.

The bumper can now be refitted and work then proceeds to the wiring of the sensors into the reversing light circuit.

To find the wiring relevant to the revering lamp circuit, remove the reversing lamp bulb and mounting from inside the boot lid. Identify the wire feeding the centre of the bulb (12v switched live) and trace this back down/out of the boot lid. In my case it was initially black, changing via a plug connector after about 4” to RED/BLACK STRIPE. I can’t be certain of other models & imports, but it’s easy enough find out for yourself.

This was the feed, via armoured cabling protector, that is then easily found in the boot (just follow the cabling) ……….

Right-hand side of boot. Look for the red wire with black stripe.

You will need to remove a small section of the insulation tape to free up a decent length of RED/black wire to scotch-lock onto. This is the 12v feed to the reversing sensor, which will become live when reverse is engaged. The only other wire to connect is your GROUND, which I chose to screw into the chassis using the fixing for the WHITE plug connector seen in the photo (10mm socket).

The wiring can then be easily fed inside the car by following the main loom, which feeds the rear. You will need to partially remove the rear seat, but this is only one bolt (10mm socket).



There are 2 lugs at the front of the bottom seat section, at each of the left & right seat positions. Pull the seat up at the front and it will pop out.

Pull back the carpet to reveal another 10mm bolt, which you need to undo.

10mm bolt fixing backrest to rear seat.

Where you go from here is simply a matter of personal preference, depending on where & how you want to mount the actual bleeper/display.

I chose to mount mine at the side of the parcel shelf, behind the rear, nearside seatbelt feed. (there must be a name for this area, but I can’t think of one!)
This is discrete & out of sight, coming to your attention only when you actually reverse. It can be seen either in your mirror, or whilst looking back. The other side (which would have been an easier fit) is obscured by the driver’s headrest. Some with the more fancy digital displays may want them on display in the cockpit area. Each to his own there really.


Bleeper/display unit mounted at rear of n/s seat belt feed.


The wiring, after threading through from the boot, is simply pushed behind the seat back and the parcel shelf. No need to remove the complete seat back as there is play in it due to the upholstery.
I then fixed the display/bleeper to the roof-lining material using 2 strips of adhesive backed Velcro. The main reason being that it could be moved should the positioning be found to be inadequate, without causing any unsightly holes. It also fits very flat.


Road testing the sensors, I was getting a single tone (indicating less than a foot) at this distance.