Parts:
• Witson® LED Display Car Vehicle Parking Reverse Backup Radar System with 4 Parking Sensors (£11.99 from Amazon)
https://www.amazon.co.uk/Witson®-Display-Vehicle-Parking-Reverse/dp/B017GZREAU/ref=sr_1_4?s=electronics&ie=UTF8&qid=1470234323&sr=1-4&keywords=parking+sensors
• Cable ties
• Paper templates (attached)
Tools:
• Small Flat head Screwdriver
• 10mm/12mm spanners/ratchet
• Drill
• 22mm wood drill bit and drill bit supplied with above purchase
• wire cutters
• soldering iron
• largish round/semi circle woodworking file
• masking tape or frog tape
Time:
1.5 – 3 hours
Steps:
• Remove all the contents of your boot
• Remove the rear hidden box. There should just be a couple of retaining clips that can be popped out with a think flat head screw driver then just pull (also remove the two clips for the rear lip cover as this’ll be coming out also)
• Remove the plastic lip cover, can be done with fingers and pulling
• Remove the left hand side flip up lid, unscrewing the nuts on the front, then leaning the lid back to reach the nuts underneath
• Next remove the left hand side hidden box, by unscrewing the nut at the bottom by hand and removing the retaining clip. This should pull out easily by hand
• The wiring harness along the left is where we tap into the reverse light feed. Also remove the rubber grommet in the floor and save for later.
• Pull out the wires and locate the reverse light 12v supply wire. On the rx400h it was grey, I believe on rx300/350s this might be red. However if you’re unsure use a multimeter to test.
• Strip a section of the wire and solder on the red (positive) wire for supplying power to your control box. Insulate with electrical tape
• Ground the black wire (earth) for the control box power. I connected it to a bolt on the rear of the boot where there were other earthed wires. 
• At this point, I tested the reverse sensor was getting power when the vehicle was put in reverse by plugging in all the components
• Next, to fit the sensors. I think most people would remove the bumpers to attach these. However, I was able to fit them with the bumpers in place. That said I have small fingers and wrists.. and was only just able to. Other might find it easier to remove the bumper at this stage.
• I found these templates and attached them using frog tape.
• Now using the supplied drill bit, carefully drill the holes in your bumper
• Behind the plastic is foam padding/strengthening. I used the 20mm wood drill bit to drill though this and created a hole big enough to get my finger in from the inside
• Use the round file to smooth off the lip around the hole.
• The sensors supplied with my kit needed a small flat screwdriver inserting to push 4 tabs in to release the back of the sensor. This allowed the rubber tabs to move back a little. The idea is you push the sensor into the drilled hole, then push the back on and it secures the sensor. This was by far the fiddliest bit of the install. However, I think it might possibly have been easier to forget about using the rubber clips and just glued the sensors in place. Those without patience might prefer to do this!
• Once all sensors are inserted and secured. Thread the wires along the inside of the bumper, securing with zip ties where possibly.
• Locate the underside of the hole where you removed the rubber grommet and feed the wires through. I managed this without removing any trim from the other side. I just used some garden wired and treaded it through from the top.. then tied this around the sensor cables and pulled it through.
• Once all the cables are back in the boot. Drill/cut a small hole in the rubber grommet and thread them through this. Pop the grommet back in the hole and I used some insulation tape to create a seal.
• Now finally choose a location for your beeper/display. I put mine next to the centre cup holders as I didn’t want them too visible on the dash. However, it would work well on the dash or even on the rear view mirror. If you prefer you could even mount near the rear screen as you may be looking back that way anyways (this would be easiest place to run the wires to as well!).
• Once fixed. Find the best route and run your wires under carpets and trim into the boot. My route left me only just enough length on the wire so it was cutting it pretty close!
• For information, I went back into the centre console, under the carpet in passenger foot well, underneath the front and rear kick plates, and up underneath the hidden compartments. It was actually easier than I thought and didn’t take too long. I had to use the garden wire trick in one or 2 places.
• Now plug the screen and 4 sensors into the control box. The shortest sensor cable should be position D, then C, then B and then A (if you’ve gone the same route as me).
• Attach to the side wall of the boot where you feel there is room and finally attach the power.
• Now replace the left cubby box, the flip up cover, the rear plastic lip cover, the rear box and any other trim you might have removed.
• Test the sensors by parking near some vehicles or wall. I found the reverse camera red line gave me about a foot and half distance from the object, the reverse sensor flat line beep, just under a foot.
• For £12 I think this is a super cheap mod and very useful to have the extra distance reading and bleeper. You get what you pay for however and the bleeper does sound cheap. Luckily there is a switch to turn in off from the screen incase the baby is sleeping. I might open it up and install a small Potentiometers in front of the speaker to give it a volume control at some point. However, to be honest, I don’t find it that annoying yet.
RX300:350:400 Reverse Sensor Templates Left.pdf
RX300:350:400 Reverse Sensor Templates Right.pdf
