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Trailer Wiring Harness Installation - 2016 Subaru Legacy

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How to Install a Trailer Wiring Harness on a 2016 Subaru Legacy

Today on our 2016 Subaru Legacy, we'll be installing the Tow Ready T-1 Connector Assembly with Upgraded Circuit Protector Module Light. Part number 118671. The first thing that we're going to want to do in order to install our trailer wiring is to pop our trunk. If your vehicle is equipped with these cargo nets, you want to unhook them on either side and lay them out of your way. Now, we'll want to remove this trim panel piece that's above our bumper. To do that, start to unscrew the cargo net hooks. One on either side.

There's a spacer there, too, so make sure you remove that. We'll also take the spare tire cover and pull it out, so it's out of our way. We'll set it aside. Pretty much right in the center of the trim panel piece, there's a plastic clip that helps secure it, just take a trim panel tool to pop it out. Now, we can remove our trunk panel piece by pulling it towards the front of the car, like so. We can set it down out of the way.

We'll want to take the other cargo hook that's near the top by our taillight assembly on either side. Unscrew those. Take the spacer off again. We'll do the same thing on the other side. Now, we'll take our carpet, pull it back so we have access to our taillight and the wiring.

We'll do the same on both sides. On the driver's side, the connector right here, we'll press on the locking tab that's on the top of it and separate the connector. There we go. Okay. We'll do the same thing on the passenger's side now. Now, we'll take the yellow end of our quick connect fittings, put the male end to the yellow end, click it in to the factory wiring.

Then, we'll plug it back in to our taillight assembly, just like so. We'll take the green wire and do the same thing on the passenger's side. We'll make the male end, plug it in to the factory wiring, and then plug the female end into the taillight assembly, like so. With the Styrofoam piece that covers up the spare tire removed, we can remove our spare time now by turning it counter clockwise. Pull the spare tire out, and get it out of our way. There's this grommet towards the back of the spare tire well. We can pop it out of place by pulling up on it. We can drop down our four way flat trailer connector through that. We'll mount the control module using the provided double-sided tape over here on the driver's side to a flat surface. Peel back one side of it, stick it on the module, peel back the other side, and we'll stick it down. Now, with the provided 1/4" self tapping screw, we're going to ground out our ground wire, which is this white wire with the ring terminal to the body of the car. We're going to take the black wire coming from our control module, which is the power wire and strip off a little bit more, so we have something to crimp our butt connector to. We'll take the included butt connector, stick it on the wire, and crimp it into place. Now, we'll take one end of the black wire, that was included in the kit, and feed it through the hole where the trailer wires go through the bottom. Take the other end of the wire, strip off about a 1/4", and connect it to the yellow butt connector going into our control module, crimp it into place. I want to take some electrical tape here and wrap it over our connection we have between the power wire and the control module, just in case any moisture we're to get around it this will help protect it. Now, we'll take our grommet that we removed and a pair of side cutters. Cut a slit in it, go diagonal a little bit, this way the wires will have a place to rest. We'll insert the power wire to the slit and the wires for the trailer connector, and we'll reinstall the grommet pushing down on it, and we can seal our slit up with some black silicone sealant. That will keep any moisture or dirt and debris from entering the car. Put a nice healthy bead on it, push it down around where the wires are. With all of our connections made inside our trunk, we can start putting it back together. Start by folding our fabric back into place. Take one of our spacers, put it back on, and the cargo net hook, screw it into position, and do the same on the other side. Now, we'll reinstall our spare tire. We'll put back our spare tire tools, set them down in position, like so. Reinstall our center trim panel piece, push it down into position. With our center trunk panel back in place, we can reinstall the plastic spacer and the cargo net retainer, screw it into position. Now, we'll reinstall our plastic push pin retainer. Just push it into the hole. You may have to persuade it in a little bit. Our panels properly secured. We'll reinstall our trunk floor liner and reattach our cargo nets on either side. Let's go ahead and get our pull wire that we're going to use to pull the wire up from underneath the car once we have it routed, situated so it's already down there. I'm just using a piece of air line tubing I have laying around. You can use a coat hanger or anything that's fairly rigid to do that. I'm just going to go as close to frame rail as I can behind this wire here next to the brake booster and squeeze it down between the frame and that brake line. I should be able to grab it from the bottom. All right. Now, we're going to start routing our wire to the front of the vehicle. I'm going to go ahead and do that. Once I have it done, I'll show you how we did it. We routed the wire back from the grommet and our spare tire well, along the spare tire well itself, over this bracket, and up and over the rear sub-frame that holds the differential in place, brought it down, wrapped it around this cross member here that helps support the sub-frame, so the wire doesn't mover around any. Then, we slid it along the inside edge of this black plastic piece that covers the under body of the car, coming out right here, and then to the sub-frame body connector here, wrapped around there. Now, we can attach it to our pull wire, and pull it up through the engine bay. We'll grab our pull wire and pull up our power wire. Double check that it's not going to run up against any exhaust parts or anything like that or the steering shaft, which is right there. We'll secure it with a zip tie just so it gets extra clearance from the steering shaft. We'll cut off the excess of our zip tie. Now, we'll take our yellow fuse holder that's already in a loop, cut it right in the middle, strip back about 1/4" on either end, twist the wires together a little bit, install the yellow ring terminal that's included on one end, crimp it on. Put a butt connector on the other wire, crimp that on, remove the protective cover over our battery, and measure out about how much wire we're going to need to connect to our battery. We'll cut off the excess. We'll take our power wire, strip off about a 1/4", take our fuse holder, insert the power wire into the yellow butt connector, crimp it into place, and we'll wrap this butt connector with some electrical tape. This will just help protect our connection in case any moisture we're to get inside the engine bay. We'll remove this nut, 12mm off the top of the positive terminal on the battery. Take our ring terminal, sit it over the stud, reinstall the nut, and we'll tighten it back down. Reinstall the plastic cover the best we can. Take our fuse holder and install our 15 amp fuse that's included, make sure to push it down in all the way, put the protective rubber cap on, and we'll put one more zip tie on our fuse holder here to secure it to these fuel lines just so it stays further out of the way. Then, trim off the excess. I have our four pole flat trailer connector here. Just long enough to basically reach the end of our receiver. That gives you enough slack to hook it up to your trailer that you're towing and whatnot. The excess I have zip tied behind our hitch here, just so it doesn't dangle down and drag on the road. Now, we're going to test our electrical connection and make sure everything functions on our trailer connector. This is a four pole flat trailer tester here. It's Part number 126 on our website if you would like to purchase one. Plug it in, and I'll start running the functions on it. I'll turn the headlights on, and our brown wire light should light up indicating we have proper taillight function on our trailer. I'll do the left turn signal, and the yellow wire light should light up. I'll do the right turn signal, and the green wire light should light up. I'll step on the brakes, and both the yellow and green should light up. Let me turn the taillights off here real quick. That completes our installation of our Tow Ready T-1 Connector Assembly with Upgraded Circuit Protector Module Light. Part number 118671 on our 2016 Subaru Legacy.

Info for this part was:

Employee Jacob T
Video Edited:
Jacob T
Employee Cole B
Installed by:
Cole B
Employee Chris R
Video by:
Chris R
Employee Brent H
Test Fit:
Brent H

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