DIY Parking Sensor Installation 

This is a guide to installing an ebay parking sensor kit on a 2002 Peugeot 406 Saloon. It should apply to all saloons, and it an easy and cheap addition to the car.
This kit cost less than £30 and bar a mistake i made with painting they are very accurate sensors, i had them on my old fiat panda, and renault clio which worked very well, the clio has had them for 4 years and they still work without a problem.

The first issue is to find a place to place the parking sensor ECU, it needs to be close to the rear bumper, and it needs power from the reverse light, handily in the boot of the 406 each corner of the boot has ample space.

After removing the carpet on the right hand side of the boot, i found the JBL amp, and located the ecu on top of that, on other models without the amp there should be even more space, some double sided sticky tape and cable ties is what i used to secure the ecu in place:

ECU Placement and Power Supply:

This shows the best location to place the ecu, some cars have nothing here, some have this amp, some can also have a sat nav drive, regardless of that there should still be plenty of room to fit the ecu.

 Some double sided sticky tape under the ECU should help it stick into place

The power to the ECU comes from the parking sensors, i removed the plug going to the rear light cluster, and used a multimeter to find which wire sent power to the reverse light and spliced into that for the positive feed, i used the cars body to provide the earth/negative.
Note: the blue connector i used failed after about 2 months, i recommend soldering the wires together and sealing it with heat shrink as a more reliable connection:

Another view of the wiring, the power is supplied, i found a tidy place to mount the bleeper, make sure you can hear it, its plug just slots into the ecu. As you can see cable ties are the handiest way to reinforce the double sided sticky tape:

Drilling out holes

Now the next thing to do is drill the holes for the parking sensors, its the scary bit because you cant undrill holes in your bumper. I did not use a particularly accurate way of measuring the best place to drill the holes, just along the bottom lip of the bumper, this is great because there is over 30mm of flat surface to work with, the sensors have a diameter of 21 so more than plenty of flat surface to work with. Also behind this part of the bumper there is no obstructions such as impact bars.

To measure where to put the sensors as i mentioned is tricky, i got a pair of identical chairs, set them at each side of the car, i tied a string level between the two chairs which dealt with the horzontal placement. As for the vertical i measured from the ground up (the ground being a flat shed floor, and the car had nothing in the boot that would leave the suspension sitting to one side)

I used the centre of the towbar to measure the distance the sensors should be to each side of it, the first pair of sensors were below the corner of the tailight, and the second pair of sensors i got the left on to below the 'P' in Peugeot, measuered the distance and did the same on the other side.

It might be an odd way to measure, it worked for me, your free to try your own technique. Measuring this sort of thing is my least favourite bit.

With the 4 points selected with a bit of black marker i used a punch to make a small indent in the bumper, and drilled out the holes with the drill bit supplied with the sensors. Its 21mm so precisley whats needed for the sensors, and as the bumper is a soft material a basic cordless drill will get through it easily

Below shows the supplied drill bit drilling through the bumper, which leaves a neat and tidy cut that is ready to accept the sensor:

These arrows point to where i placed the parking sensors on the rear bumper:

Putting the sensors into the bumper:

With the holes drilled the next step is to put the sensors into the bumper, this is simple, slide the spacer ring through the wires and up to the sensor (easier now than later) then thread the wires through the bumper, and put the sensor into the bumper.

The spacers are shaped to give you some control over the angle the sensors face at, which is useful given that the bit of bumper the sensors were mounted onto faces upwards. The spacers correct this and keep the sensors pointed behind the car.

The spacers can be a bit hard to slide over the sensor and this is where a ruler or flat edge is handy to push them on without breaking them:

Put the wires for the sensors through the bumper first, they are also labeled A,B,C,D on the sensors, i started with A on the left side of the car, and D on the right, i dont acutally think the sensors are any different but it does no harm to put them in order:

Push the sensors on ahead into the bumper, twist them to have them facing at the right angle, then push them into the bumper good and tight:

This shows what the sensors look like from behind the bumper, its only a bit of foam that provides a tight fit to hold the sensors in, however i have had them on 2 years now and they have not fell out.

Painting the sensors:

If you buy the sensors in most cases you can choose to get the right colour from the seller, i had these matte black sensors from a car i never put them into, so i had to paint them.

I will show you how to paint them, im not good at painting things, and its probably best to get them the right colour in the first place to save the hassle, and also i found after painting the sensors (a job i actually did 2 weeks after the installation) that the sensors which worked perfectly became over sensitive indicated that the car was too close to something even when it wasn't near anything.

Anyhow here goes, The area got well masked off:

Then i thought the masking wouldnt prevent overspary well enough, so i put the sensors into these cardboard boxes to prevent overspray even better. (Now im typing this guide it would have made more sense to have taken the sensors out of the car again and sprayed them away from the car, but this was what was done):

The carboard boxes again, which worked superbly well at preventing overspray, and they also could be   closed over while the paint was drying to prevent dust getting on the paint:

The Painted Sensors:

Depending on the paint makers instructions let the paint dry, i was using the genuine Peugeot spray paint for the sensors, with two coats of lacquer (the lacquer is probably what ruined the accuracy of the sensors) However they were well painted. 

Once dried i pushed the sensors back into the bumper:

Routing the parking sensor wires:

The next job is to get the wires from the 4 sensors to the ECU in the boot of the car, the first job is to drill a hole to let the wires come into the car. You might find a unused grommet, or be able to take the bumper off and find a suitable hole. However i decided to drill a new hole.

I drilled out the new hole in the area near the parking sensor ECU, i used the 21mm drill bit to cut a hole through the boot floor. It took longer to drill the hole than the plastic but the bit did the job no problem. As you can see below, i drilled from underneath the car upwards, therefore i knew i wasnt drilling into some reinforcement bar, the wire beside it goes to the trailer lights plug:

I made sure to apply a liberal amount of Galvanising paint to both sides of this hole to prevent rust, i painted it on with a brush, not too many will see this part of the car to care about brush strokes:

I put an old grommet round the hole to stop the wires getting cut on the sharp metal, then routed the wires for the 4 sensors under the car through this hole and into the boot. The wires have plenty of length. Be careful when routing the wires, make sure to secure them tight to something solid thankfully the towbar bracket was a handy place to wrap cable ties around, its also worth taking into account the exhaust gets hot so make sure none of the wires get close enough to the exhaust to melt.

With the wires nicely routed under the car and secured by cable ties, bring them up into the car, i then put a good dollop of silicone into the hole to keep it sealed:

Now bring the 4 wires up to the ecu, plug them into the correct sockets, the Lables on the end of each wire say A,B,C,D and they meet up with the labled sockets on the ECU. It probably doesnt matter so much on this simple ECU where the wires are plugged in, but on more sophisticaed parking sensor systems with an LCD display plugging the sensors in correctly would make sure the display shows weather the obstruction was coming from the left or right. 

Here are the wires going into the ECU:

Tuck the wires neatly into place, there is a lot of excess wire, i didnt want to cut them because the wee plugs look flimsy, and I dont even know if they can be cut and shortened correctly (the instructions may have said not to cut the sensor wires). Anyhow i tidied up the 4 wires and put the boot carpet back in place, its impossible to see any of the wires or ECU with the carpet back in place:

The Finished Sensors:

The sensors worked great before i painted them, after painting as i said they would scream that something was behind the car when there wasn't, its worse in the wet. Given the cheap cost of a kit i really should buy already coloured sensors and plonk them into place, the ECU can stay as most parking sensor kits off ebay are the same.

Here is the installed sensors: