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Trailer Wiring Harness Installation - 2013 BMW X3

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How to Install a Trailer Wiring Harness on a 2013 BMW X3

Today on our 2013 BMW X3 we'll be installing the tilt-ready heavy duty Modulite circuit protective vehicle wiring harness, part number 119190KIT. To begin our installation we'll first need to access the manufacturer's wiring harness. We'll go ahead and remove the interior trim panel here on the driver's side. Here, just behind the tail-light housing, coming through the black grommit will be the wiring connected to the driver-side tail-light assembly. Next we'll go ahead and use the utility knife, cut back the electrical tape to gain access to the wires. Then using a test light provided with our install kit we can probe each wire to identify which signal it provides. Here in the driver-side the yellow wire with the black tracer will connect to the brown wire from our converter box. This is the running light circuit. To connect the two we'll use the quick-splice connector by putting the quick-splice connector over the manufacturer's wire into the inside groove, then feeding the brown wire into position, crimping it down and closing the clasp.

Now we'll go ahead and repeat the same process for our break light circuit, which will be the yellow wire with a blue tracer on the manufacturer's side and the red wire here on our bork-ball 00:01:20 side coming from our converter box. And then once again we'll repeat the same process with the turn signal circuit, which will be a blue wire with a green tracer connected to the yellow wire from our converter box. Now while remaining here on the driver's side we'll take the white wire with the pre-touch ring terminal, which will be the ground wire for our converter box, and attach it to the body of the vehicle. Here in the corner near the vehicle vent will be a perfect location to ground our wire with a self-tapping screw. Quick tech tip, the reason this is a great location is where the sheet metal doubles up giving us more material to attach the ring terminal too. Next we'll take the green wire from our converter box, which will be the turn signal for the passenger's side, and start routing it over to the passenger's side. We'll go ahead and remove the interior trim panel on the passenger side behind the tail assembly and then the center compartment cover.

We'll begin feeding the wire over to the passenger side. Once we get it over to the passenger side we'll remove the pushpin fastener and feed up behind the vehicle insulation. Then we can go ahead and strip back the black electrical tape and test the wires just as we did on the drivers side using the test-light provided with our install kit. Here on the passenger side you can see it's a blue wire with an orange tracer. Now we'll go ahead and use the quick-splice connector and attach the green wire to the blue wire, repeating the same process we did on the drivers side. With this connection made we can go ahead and use some black electrical to wrap our wires back up.

This will assist in preventing moisture, dirt, dust, or debris from corroding our connection. I'll also use a couple of black zip ties to secure the wiring as we route back over to the drivers side. Next we'll need to go ahead and attach a power wire to the black wire coming from our converter box. This will lead to the vehicle battery. To do this we'll go ahead and strip back both ends, attach the yellow butt 00:04:02 connector to our length of wire and then to the power wire from the converter box. Then we can begin routing our wire over to the battery. Now that we're in the battery area we'll go ahead and cut off any excess from our power wire, strip back the other end.

Now we'll go ahead and prepare our fuse holder that'll go inline with our power wire. We'll go ahead and cut the fuse holder in half and strip back both ends. We'll add out butt connector to one end and our ring terminal to the other. Then we'll go ahead and take the butt connector and attach it to the power wire we just ran from the converter box. Next we'll go ahead and take some black electrical tape and wrap up our remaining open connections. Now we can go ahead and remove the positive battery terminal cover, remove the nut, install our ring terminal, and then resecure it. With all our wires run we'll go ahead and use some black zip ties to secure our wiring here in the battery compartment. Next we'll go ahead and install our fuse into the fuse holder and then we could take our side cutters and cut off any excess from the zip tie to clean up our install look. With that done we'll go ahead and reinstall our interior trim components. That'll complete the install of our new four pole circuit. Next we'll go ahead and show you how to use it. First we'll take the four pole that'll be stored in the driver-side lower compartment and route it to the center of the vehicle and down to the hitch or accessory. Be careful to stay away from the latch as pinching the wire off the latch can harm it. However the weather stripping is thick enough that we can simple go ahead and close rear cargo door on the wire. Once we're finished using our new four pole connector we'll simply role it up, store it in the cargo area, and then reinstall the interior trim panel. That does it for the install of our tow-ready, heavy duty Modulite circuit protector vehicle wiring harness, part number 119190KIT on our 2013 BMW X3. .

Questions and Comments about this Video


I heard that you may need to do something to protect vehicles with tail light out sensors. Do you know if this is an issue on the 2013 BMW X3 35xi?

Etrailer Expert
Reply from Rachael H.

This kit would work, but I recommend using the ZCI wiring harness # 119250KIT , since this kit does not require splicing into the vehicle existing wiring and therefore negating the need to protect against the vehicle bulb out sensor. I have included and additional video link for your reference.

Lorenzo B.

Is there any concerns with the vehicle computer when setting this installation?

Etrailer Expert
Reply from Patrick B.

As long as you connect to the proper circuits, using the circuit tester to verify, the 119190 harness should not create any problems with the vehicle computer. Make sure to run the power wire for the module to the battery positive terminal. Trying to find a power source anywhere else could potentially over load a circuit and blow fuses or create a problem with the computer. On the 2013 BMW X3 in the video, the battery is conveniently located in the rear cargo area.

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