Reverse Sensor Install 2012 Mazda5

This is a walkthrough on a reverse sensor installation on my 2012 Mazda5.

I purchased this kit on-line for about $25 with four sensors.


The first thing I did was test it with a 12v source on my workbench. The beeping was deafeningly loud!
I took apart the display unit where the beeper lives.


I didn't have a resistor of a suitable size to reduce the volume, so I ended up with a cheap and lazy solution of soldering a green LED inline with the beeper. For those that are wondering, a white LED effectively mutes the beeper - too much resistance. As it turns out the green LED doesn't silence it enough - therefore it will get a simply tape over the top treatment to cut down loudness.


This is also a good time to test the 4 sensors to make sure everything works before installing anything.

I wanted to use connection points that do not cut too much into the existing car wiring. I chose to graft the 12V+ lead for the sensor kit to the reverse light wire at the hatch connector. This is behind the upper plastic cover on the hatch.




You could also cut open the insulation on the blue/white wire anywhere along the harness and splice in the power wire to it.

Since I using the connector location, I had to feed the wires through the rubber boot. It is easier to pull the wires with a thin piece of plastic to fish them through the boot - I used a large ziptie.


Once the 12v+ wire was soldered to the main connector pin, I soldered the ground wire to the existing ground mount.


The wires are then routed through the rear pillar behind the plastic trim to the jack storage compartment. Not shown is the display cable routing from the front dash to the back. This is straightforward enough if you follow the floor trim panels along the door sills.


The display location is a personal matter. I was hoping to place it in the "cathedral peak" above the speedometer. But that location is PERFECTLY useless since it is not visible due to the steering wheel location. So I haven't quite gotten this straightened out. Since the beeper is still crazy loud, I might stuff it behind the dash and forget about looking at the display.

Next up is the bumper itself.

In my case I removed the rear bumper completely. I wanted to use the factory locations and I knew there were markings on the BACK I could use.

As long as the sensor positions work correctly for you application, then it really doesn't need to be installed exactly in the factory positions. Looking back, I would have installed the four sensors closer together across the flat section. The factory positions for the outer sensors point a bit to the corners.

It is also possible to install the sensors WITHOUT removing the bumper. But routing the wires may be tricky without know what is back there.....the foam block is the key obstacle.

I won't go through the bumper removal process here, but it is noteworthy that the taillights need to be removed to do it.

For the factory positions, the two middle sensors will not clear the foam block as it stands. So the corners need to be cut back a little to allow the sensors to sit flush to the bumper skin.


I drilled a pilot hole to allow for a more controlled cut with the hole saw. You have to drill from the BACK of the bumper if using the factory position markers.

Masking tape on the outside of the bumper protects the paint during the hole saw cutting. I used the hole saw on the outside - which is how it would be used anyway if the bumper was not removed.

The kit included the hole saw. It was a piece of junk that was not concentric - it wobbled a lot. But it did cut effectively. I would recommend using your own hole saw or step drill bit if you have it. Make sure not to push hard on the bumper while drilling. When the hole goes through, you don't want to bash the drill against the bumper.


I pushed the sensors PARTWAY on the bumper to allow for fine adjustments after getting the bumper back on the car. I made sure to label the 4 sensor wires so I knew which order to hook them up to the control box.


This hole under the jack storage area is covered by a plastic grommet. I drilled out the center of the grommet to feed the wires through. Note that the farthest sensor wire will barely reach the control box in this position.


Then after securing all the wires neatly with zipties, the system is ready for fine tuning.


I still needed to cut out some more foam once the bumper was installed since the sensors still would not go in all the way flush. And the rotation of the sensors greatly determines the area it is detecting.

The kit is a cheap solution for parking assistance. It is not perfect, but it easily and accurately detects walls, cars, and other large objects.

It does not easily detect curbs (too low) or thin objects like a small sign post.

The biggest limitation of the sensors is they have a VERY narrow detect field of view. So if you space out the sensors too much, you will have dead spots in the detection field. My suggestion is to place the four sensors closer together as practical across the rear and forget the corners. Higher quality sensors will have a wider field of view.

The narrow beam characteristic has one great benefit - it is VERY accurate at detecting at close distances. You can confidently use the display to park the car down to 3-4 inches of a wall or another car (display reads 0.0m at this range). You'd want to park at 0.6-0.7m (approx 1.5-2.0ft) so you can open the rear hatch.