Trailer Wiring Harness Installation - 2016 Mazda CX-5

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How to Install a Trailer Wiring Harness on a 2016 Mazda CX-5


Today on our 2016 Maxda CX-5, we'll be installing the tow-ready T-One vehicle wiring harness, part number 118568. Now to better assist us in our installation of our wiring harness here, we'll be using part number 18136 and 18144 available on our website. These are couple brackets that we can use to externally mount our 4-pole flat trailer connector to our hitch. Here's our 4-pole flat connector installed on our vehicle. The reason you want one of these is so you could tow a standard trailer and have all the lightening functions required by law. This is a standard 4-pole flat. We have our turn signals, we have our tail lights and we'll have our brake lights.

Now that we've gone over some of the features of the 4-pole flat trailer connector for our CX-5. We'll show you how to install it. With our hatch open on the back of our Mazda, we'll start our installation by lifting up the spare tire cover here, pulling it back, locating our plastic push pin fasteners hereon the sides, pulling out the center, then pulling out the pin itself, we'll do that on both sides just like so. We'll pull up on our trim panel here to remove it. On the side panel here, we'll notice two more of those fasteners, one on either side. Do the same thing like so. Then on the side, there's these cargo loop tie downs.

We're going to remove those as well, so to pop them up, just cut down here at the bottom of it, on the side. Pop it up, do the same on both sides. Just like that. There's two 10 millimeter bolts, one of the other side, we need to remove those as well. Set those aside. We'll take these panels out around our spare tire and set them aside as well.

We'll take our side panel here and pull it out towards us somewhat. Now for our panel to pull back slightly, pop out this side access panel here on the driver's side, like so. We will gain access to our wiring connector. Now with our panel removed, we're going to unplug the break light bolt here and the turn signal bolt here. We will take your yellow and white connectors here as well as our brown read and white connector here. We'll feed them from behind like so out through our panel so we can grab them and our connector here though will go to our control module, we'll feed back there as well.

Just so it's readily available when we need it. Pull that through along with our ground wire, and we'll have our connection too for our power wire. Leading our 4-pole trailer connector here down the trim panel, same with our green wire, and connectors that will go over to the passenger side for that turn signal. Now we can make our connections on the driver's side, we'll take our 4-pin connector here which ones are our brake light and taillight bulb. We'll connect it to the male end, this 4-pin here. We'll take the female end on the tow harness, pull it back into the bolt, we'll do the same thing to our turn signal bulb. Just like so. Untangle all the wires. We'll grab our control module which has double sided tape already mounted on it, plug in our control module so it snaps into place. Remove the double sided tape and then we'll mount it to a flat surface behind our panel here, right about there, push it into position. That help us gain access to this panel a little bit better, so we can run the wires out to the bottom. Remove the Philips head screw that was located here and our spare tire cover completely. This back carpet snapped in, three pieces on either side, three little snaps there, and there's two in the middle, pull on it, and it pops right off, and now we have full access behind our panel to run the wires down to the bottom. There's a grommet right here on the floor, we're going to be removing this grommet to run our trailer connector down through it and run our power wire up through. Let's grab the grommet, pull up just like that, and now we can take our 4-pole flat trailer connection just like so and we'll drop it through our vehicle's floor and we'll feed it out the bottom. Now we'll take our power wire, unravel it all. Once we have it all unraveled, we'll take one end and strip off about a quarter inch of the insulation from the wire, just like so. We will twist our wires together, insert it into the yellow butt connector like so. We'll take our crimpers and we'll crimp it into place just like so, give it a tug to make sure it's not going anywhere and then we'll wrap out butt connector in some electrical tape to provide a secure weather proof connection. We'll feed the other end of the black power wire there we'll run a route up to the engine made a connect to the battery through our hole. We'll go down through the same grommet we passed the 4-pole trailer connector through, pull it out from underneath the vehicle and now with our wires passed through, we can take a grommet and cut a slit in it to slide them through, go diagonal on it a little bit so the wire has a place to rest. Insert our 4-pole flat and the power wire into the slit, that'll push the grommet back into position like so and we will seal the hole that we made with some black silicone just to keep any moisture, dirt and debris from entering the vehicle. We'll take our black silicone and we will put it down into our grommet. Making sure we get a nice good coating on it. It will just take a few hours to dry, so you may want to park your vehicle on a garage for it to fully cure so you don't get any moisture in there. Now with our provided quarter inch self tapping screw, we can secure our ground wire to the vehicle's body. Grab our white wire with the ring terminal on it, that's our ground wire, put it over the self tapping screw, with that held in place, we'll secure into the body over here. Now for panel on the passenger side, remove the same way as the driver's side. We'll feed our wire out and behind the panel. We'll take our turn signal connection here. Remove it. Plug in our tow package on it and then back into the turn signal. Now with our connections all complete in the hatch area. We can go ahead and put our panels back on. Want to make sure our leather stripping sits on the top of the panel like it did originally. Reinstall our cargo hooks too. Just snap them into place. Reinstall our 10 millimeter bolt. Put the cover back down and we'll do the same on the other side. Now we'll secure our green wire that gross across from the module. We'll secure it with a couple zip ties to this factory wiring harness, just to help pull it out of the way for many of the snaps that hold the trim panel on place. We'll cut off our excess zip ties. Before we reinstall our trim panel, we need to put the two push pins back in to hold the side panels in place. Push in, grab our trim panel here. Line it up. Push it down till it clips in. Grab our leather stripping again. Pull it on top of it. Just like so and then we'll reinstall the two push pins that held the trim panel in place. Now I can reinstall our spare tire cover, just slide it back into position. Pull up our carpet, and now with our front half folded down, we'll snap our carpet back into it, with the push pins. Three on either side, just like so. Now our installation in the trunk is complete. We can close it up. Here with our carpet snap back into place on our mat, reinstall our toolbox here on either side, just like so, and we'll fold our mat down into position. Our installation is now complete in the back. Now we can run our power wire to the front. We have wire zip tied here to the fuel line, it goes up to the engine bay, goes back on underneath this black plastic air and water deflector towards the back, up over the rear sub frame, making sure we avoided any moving parts and avoided any sources of heat such as the exhaust and then it goes, pulling over the sub frame up to our grommet where it goes inside the vehicle. Now we have to tape it to our pull wire here, we're going to go to the engine bay and pull that through. Here on the engine compartment, we'll have a good place to zip tie our excess wire and then we can make our connections to the battery. Take out about a quarter inch of insulation on both ends of the fuse holder, twist our wires together so that it go on to our terminals nicely. Put a ring terminal on one end and we'll crimp it into position. Put a yellow butt connector on the other end, crimp it into position as well. Now we'll strip off about a quarter inch of the black wire we routed from the back, twist the wire together on that as well insert that into the end of the butt connector on our fuse holder, we'll crimp it into position. We'll wrap our butt connector with some electrical tape to protect it. Double up on under hood connections just to better protect them because it is exposed to more heat than on other locations at the car. Right there, we'll make a good connection for our fuse holder. Let me grab a 10 millimeter socket and we'll remove that nut, with our nut removed, we'll install our ring terminal right there, and install our nut, and we'll tighten it down. Let me take our plastic cover here and reinstall it. Just like so. Snap back into position. With our fuse holder tucked up out of the way, pull it up a little bit and install our provided 15 amp fuse. Just like so. Put our dust cap over the fuse holder. We can slide it back down into position down here around the battery box. We're bending one of our brackets here to make our connection for our trailer harness, stuck it in the vice, and we'll bend it into position. With our bracket bent here, about 90 degrees, we can go ahead and attach it to our hitch. We stick our bracket in position here, we'll attach our other bracket with our 4-pole flat, it's going to connect to, like so. We can clamp it into position to our hitch using the provided clamp. Clamp started, we can tighten it up using our 5/16 nut driver. All right. With our brackets secure, we can trim off the excess of our clamp right there. We'll take our side cutters coming in from behind. Twist it. Take off the excess. With our other bracket, we'll drop in our provided Phillips screws. We'll take our nuts, we'll stick them over the middle holes like so, we can get them there with a wrench to hold them in position while we tighten the provided Phillips screws on the bottom. Hold our bracket up with a screwdriver, hold the nut in position with our finger on the top and we'll get our screw started. Now we'll do the same for the other one. These are actually walking nuts, so you can actually tighten them by holding them in place with your finger and they'll bite into the bracket so you don't need actually to get a wrench to hold it in place. That's not going anywhere, we have a nice sturdy connection for our 4-pole flat to reside in. We'll take our 4-pole flat trailer connector here, push it through our bracket until the ridges come out on the top and bottom like so, and we'll slide our dust cover over. Now we can grab our excess wire, and tuck it up behind the bumper like so and hold it in place with a couple zip ties. Trim off our excess zip ties, just so nothing can be seen underneath the vehicle hanging down. That completes our installation. Okay, with the wiring installed. With a help of an assistant and the vehicle to run the lights, we'll remove our connector here and plug in a 4-pole flat tested, part number I26 available on our website if you'd like to purchase one. Plug it in. We'll have our assistant try on the headlights. You can see it indicated that our tail lights on the trailer will be working. We'll have our assistant do a left turn signal, now a right turn signal, now our assistant will step on the brakes, and they both light up at the same time, and are lit solid, so that indicates all of our functions on our tow vehicle will be working properly, and that completes our installation of a T-One vehicle wiring harness part number 118563 on our 2016 Mazda CX-5.


Questions and Comments about this Video

Carol R.

hello graet video . got a question why is it that on my cx5 2016 the trailer harnes fuse blows when i put the car in drive other then that everything works great wit or witout trailer fuse keep blowing in harness if its in park light works A1 . please help me ive change the box and still the same 102537

Reply from Jon G.

Do your running lights come on when you put your CX-5 in drive? It could be that the fuse blows because your trailer lights are pulling too much power. If you have this T-One # 118563 installed then it can handle 7.5 amps for the tail lights and 4.2 amps for the stop/turn lights. 75472

Reply from Carol R.

@JonG hye again running lites do come on . Its only when the car start going forward thar the harness fuses blow . Nobody ever saw that trust me one dealer wit 40 yrs in business can figure it out . 75481

Reply from Jon G.

@CarolR Oh wow. So there still might be a little hope for you. If you can afford to disconnect a few of the running lights on your trailer or change them to LEDs which have a lower draw then this could possibly keep it from blowing. 75505

Reply from Carol R.

@JonG it blow a fuse on harness if or if not the trailer is hook up . Like I said when I'm in park all the lights work as they should its when i PUT THe car in drive and start going forward i do 20 fts and the fuse blows on harness . Wit or without a trailer 75510

Reply from Jon G.

@CarolR If it's the fuse that comes on the T-One # 118563 then either the ground connection is bad or the unit is deffective. 75512

Reply from Carol R.

@JonG grounds good and I've change the unit for another new one . Everything works like should but when I start going forward the fuse blows , I've try wit daylight disconnected same issue I can engaged car in drive n hold my foot on brake its Allgood everything works but as soon I let go brake n go forward 20fts the fuse blows , I'm in it 25 fuses so far had a few mechanic look at it n nothing . Thx for your time 75513

Reply from Carol R.

@CarolR any answer 75517

Reply from Jon G.

@CarolR I honestly have no idea at this point. If your ground is good and you've used multiple harnesses then you've either gotten really unlucky and received 2 bad harnesses (unlikely but not unheard of) or there is something else going on with your vehicle wiring and you're going to need to take it to a Mazda expert to have them install the wiring. I wish I had more insight but there is only so much troubleshooting I can offer until the wiring has to be looked at inch by inch really. 75519

Info for this part was:

Test Fit:
Joe V
Test Fit:
Brent H
Test Fit:
Shane H
Video by:
Andrew K
Video by:
Kathleen M
Video by:
Dustin K
Installed by:
Jeff D
Video Edited:
Jacob T
Video Edited:
Sue W
Video Edited:
Chris R

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