Curt Vehicle Wiring Harness Installation - 2018 GMC Terrain

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How to Install a Curt Vehicle Wiring Harness on a 2018 GMC Terrain


Ryan: Hey everybody, Ryan here at etrailer. Today, on our 2018 GMC Terrain, we're going to be taking a look at and showing you how to install the Curt vehicle wiring harness. So, these Terrains are really good all around versatile SUVs and that's why people use them for a little bit of everything. And the trailer wiring, what that's going to allow you to do is hook up to your trailer, illuminate the lights to not only be safe and legal, but allow other motorists around you to know your intentions as you're going down the road. And one thing people don't really think about is that some accessories, particularly cargo carriers, for example, actually have lights on them and can be lit up at night as well. And many times they're going to have the same connector that we do here.

So, this will also work well for that.The great thing with this one is that it's going to utilize your factory tow package. So, more or less, this is going to plug right in. So, why bother having to run extra wires and doing all that work when the factory's already done it for you Now, something that I do want to mention is that all the Terrains are not going to be equipped with that factory tow package. So, that's something you definitely want to check. It's really easy to find out on your driver's side, just behind your bumper.

There's going to be a plug there so you can take a peek up there and make sure you have that plug. The wiring is going to be really well-built. And that's a good thing, especially since this is going to be mounted outside. Now, the kit does not come with a bracket like we have here today, but if you need one and like this setup, you can find multiple different type of brackets that will work good for you here at etrailer.We are going to have a nice thick, rubber plug or cap rather that's going to help keep these terminals protected from the elements, but to go a step further I do recommend from time to time is applying some dielectric grease to them terminals and that's really going to do a great job of preventing any corrosion, that way we know our wiring will work for a long time. But at the end of the day, a great way to utilize what the factory has pretty much already given us and because of that, the installation is going to be really straightforward.

More or less, we're just going to have to plug it in, route our wiring over here where we want it and secure it all down.To begin our install we're going to be here at the back of our Terrain and what we're going to need to do is locate our factory plug. It should be on the driver's side behind our bumper right here in this area, but to make life a little easier, to get our hand up there and see, we're going to remove this Torx bit screw using a T-15. We'll pull that out and then we'll be able to work that back a little bit and get in there easier.So, underneath the car in that area we talked about, you pulled out on the fascia, we'll be able to find our plug. You can grab it and pull it down. It's going to have a dummy cap attached to it, just to help keep it protected, but since we're going to plug into it, we need to remove it.

It's going to be a red tab. Pull down on it and then push down on that center tab. You can pull the two apart and then from there we can grab our new wiring and simply just plug it right in. Line it up, plug it in and push down the red tab to keep everything secure.So, what I went ahead and did is just routed and secured our wiring. This is what it looks like. Just used a couple zip ties to hold it up to this bracket here. And then I just ran our four-way flat to the bracket that's on our hitch. So, I went ahead and just took a piece of wire loom and put it over our wire just to help clean up our install look. If you need some of this wire loom you can find it here at etrailer. But now since we're done down here, we can go ahead and resecure the bottom of our fascia here.So, I routed our four-way flat connector into this bracket. And if you need a bracket to do the same thing, you can find many different types here at etrailer. Now, what we can do is open up the hatch of our Terrain, come over here to the driver's side panel and make sure that we have our relay in place. So, this will be this little cutout here. You can just grab it and pop it out. And chances are pretty good that you're going to have this factory relay in already. But if you don't have that relay in, the kit does come included with two relays and if you look in the instructions it'll indicate to you where to put them. They should be in these slots right here.Now, it's a good idea to test our wiring out to make sure it's working properly. You can use a tester like this or just plug into your trailer. We'll go ahead and try our left turn. Our right turn. Our brake lights and our running lights. And that'll finish up our look at and our installation of the Curt vehicle wiring harness on our 2018 GMC Terrain.


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Employee Joshua S
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Employee Dustin K
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Employee Aidan B
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Employee Jacob T
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Employee Chris R
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Employee Cole B
Installed by:
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Employee David F
Installed by:
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Employee Brent H
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Employee Robert C
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Employee Ryan G
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