Tekonsha T-One Vehicle Wiring Harness Installation - 2020 GMC Terrain

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How to Install the Tekonsha T-One Vehicle Wiring Harness on a 2020 GMC Terrain

Rob: Hey everybody. It's Rob here at etrailer.com. Today, we're going to be taking a look at the Tekonsha T-One vehicle wiring harness on our 2020 GMC Terrain.Now, our Tekonsha wiring harness is going to provide us with a four-pole flat trailer connector so we can have all the required lights to get down the road safely, like our tail lights, our turn signals, and our brake lights. Now the four-pole connector is going to be one of the most common connectors you find on trailers, but it's also really easy to hook up a lot of different accessories. Trailer wiring is not only good for trailers, it's really good for a lot of different accessories. If we have a cargo carrier that happens to have a light kit, or maybe we just have a hitch cover that's lighted up, most of them are going to use a four-pole connector and it's a lot easier to wire it in and just plug it in than cut and splice into the factory wiring.And there's another really nice thing about our wiring here.

It is designed for the tow package, so there's no cutting or splicing of the wires on our Terrain. It's just going to simply plug in and provide us our connector right back here.Now one thing to keep in mind, it is designed to stay on the outside of the vehicle, which is nice because it is going to be right by our hitch, ready for us when we want to use it. So we do have the option to just take the dust cover, loop it around the safety chain connection point, and that'll keep the wire from dragging the ground. However, I recommend adding a bracket, just gives it a nice cleaner look and it takes up all this slack.Now here at etrailer.com, we get a lot of questions about the wiring for our Terrain, because again, this is made for the Terrain that has the factory tow package, but there is a separate wiring kit if your Terrain does not have the tow package. The big question is, is how do I know if I have it or not Our wiring kit is going to come with the harness that plugs in on the outside.

However, it's also going to come with a few relays in your kit. The relays are going to go inside the cargo area in here. We're going to have this panel right here. You may be able to get it with your fingers. You pop it up, just clipped into place.

We'll pop that loose. Now, if we look at the top section where we have this relay, we'll see that we have two open spots and that final gray relay is in the number three spot.Now, if you have a relay in the number three spot, you won't need the relays that are included in the kit. However, if you look in spot number one and two, there's actually no terminals in there at all, and we can take the included relay in the kit, and you can see that even if I do try to plug it in, there's no pressure. There's no connection. It's not making a connection there.

So the way to tell if you have the package is if you have a factory relay in spot number three. Now, if you have no relay and no pins inside any of the terminals, then there is no factory tow package.But now that we know where the relays are located and to find out if we have that factory tow package, let's go and show you how to install the outside section of the wiring, because it is really straightforward. It's just going to plug in, but it's hard to reach. So we'll make sure to show you exactly where it is.To begin our installation, we want to come to the very back of our Terrain and we're going to be working towards the driver's side, but close to the center, pretty much right at the end of the muffler here. Now, if we come to the bottom of the faciei, we are going to have one screw here. It's not completely necessary to take it out, but it will give you a little bit more flexibility to get your hand up in there. So I'll take a T15 Torx bit. I'm going to pull that screw out.Because where we're going is we're going to go right above the hitch here, and there's going to be some wiring up underneath, behind this panel. There is a dummy plug covering up the wire, so we don't get it damaged, but I will let you know, it is a little bit of a tight fit to get your hand in there. The plug we're looking for again is going to be right above the exhaust hanger towards the driver's side. Now there is a little red tab on it. You want to pull it away from the plug. We want to squeeze the tab so that we can separate the connector. Again, it's a little bit of a tight fit trying to get everything in there but we've got to get that plug loose so we can plug in our new wiring.So here's what the cap looks like. It's a little bit easier to see now. You can see that red tab needs to be slid away. Then we're going to press down on that black section and then separate the two connectors. Now we.Re going to grab the harness and you can see it's going to match the plug and be exactly the same, except we don't have that red locking tab on there. Just want to make sure we plugged this into the harness and it locks in place. I'll feed my wiring up, plug it in. You can hear that click. And I always like to give it a quick tug to make sure that it's not going to come loose.Now all we need to do is figure out how much wire we want to leave on the outside towards our hitch. I like to just take the dust cover, hook the end of the connector on it. That'll give me an idea of how much wire I need, and then we just take a few zip ties and tie up all the excess. I like to tie it as high as we can get it above the hitch behind the bumper, so I don't have to worry about the muffler heating up and having any kind of damage happen to a wire.With our wiring plugged in, I'm going to go ahead and put that screw back at the bottom of the faciei, and then can test our wiring and make sure all the circuits are working properly. So I went ahead and plugged in my four-pole tester so we can verify all the circuits. You can see when I turn my headlights on, the tail light function is working, as well as the left turn signal, the right turn signal, and the brakes. All we have left to do now is hook up to our trailer and hit the road.

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Info for this part was:

Employee Joshua S
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Joshua S
Employee Jonathan Y
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Jonathan Y
Employee David F
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Employee Aidan B
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Employee Jacob T
Video Edited:
Jacob T
Employee Chris R
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Employee Cole B
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Employee Robert C
Test Fit:
Robert C
Employee Ryan G
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Ryan G

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