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Trailer Wiring Harness Installation - 2018 Audi Q5

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How to Install a Trailer Wiring Harness on a 2018 Audi Q5

Speaker 1: Today, on our 2018 Audi Q5, we're going to be taking a look at showing you how to install the Tekonsha ZCI Circuit Protective Vehicle Wiring Harness, with four pole flat trailer connector, and insulation kit. Part number 119250KIT.Here's what our wiring looks like once we have it installed. It's going to give us a four pole flat trailer connector, which is going to give us our tail lights, turn signals, and brake lights to get our trailer down the road safely. It is going to live on the inside of the car, until we're ready to tow. It's actually going to stay inside this compartment, right here on the back half of our hatch. When we're not using it, we can just tidy up the wires, and put it inside of our compartment.

Close it up, and you won't even see anything, won't even know that they're there.What I really like about this wiring is the fact that we're not going to have to cut or splice into any of our factory wiring. We're going to have a clamp style connector, that's going to wrap around the wire and pick up the signal going through it. So, we're not going to have to worry about cutting, connecting anything. It's just going to go right around the wires, and pick up the signal that way. That way we don't have to avoid any of our warranties on our car, or get into any electrical things, if you feel uncomfortable cutting and splicing into it.Now that we've seen what our wiring looks like once it's installed, and going over some of the features, let's show you how we get it installed.

To begin our installation, you're going to want to open up your rear hatch. Just for a reference, this panel right here will pop out. Then we can have access to the wires that are going to our tail lights.Now, one thing I do want to mention. When we begin to test our wires, the hatch needs to be closed, because our lights do not work if the hatch is open. Now, to pop these panels out, I'm going to take a plastic trim panel tool.

I'm just going to come to the edge, and pry down slightly. That will release these clips, then we can see we have access to our taillight harness here. Now, we're going to do that on both sides.I have my multimeter here. Now, your kit is going to come with a light tester, this is going to do the same thing. It's just going to verify that the voltage is correct on the meter for me.

We have our headlights on right now, which means our taillights are going to be working. We're going to go through each wire, until we get right about 12 volts.Our meter here, or on your tester you're going to have the end of your light tester, light up. We're going to go through and check each one of these wires programming it from the backside. That way we don't have to cut or splice into anything. Now, we are getting some voltage, but that's nowhere near enough for the light to come on. We can see here, I'm getting almost 12 volts. My car is not on, so that's okay. And my testing probe is inside the gray wire. We're going to want to write that down.That the gray wire, on the drivers side, is for our tail lights. Now that we've found the tail lights circuit, on the drivers side here, we're only going to need that tail light circuit on the drivers side. But, we're going to need to find our left turn signal, and our right turn signal. And we're going to repeat the same process. Checking each pin and wire to do so.Now, as far as our left turn signal, we are getting a signal on the blue wire, and the black and white wire on the left side. But, we have two different sets of lights on the outside. We have the regular incandescent bulbs, and an LED strip underneath. Now, we're going to go ahead and move to the brake signal, and see which one operates that one set of lights.Now, our brakes are going to be on the same circuit. But, as a I mentioned before, only one of those lights is going to come on at the same time as the turn signal. We need to figure out which wire is just the brakes, and which one is also connected to the turn signal.I'm not getting any voltage out of the black wire, while somebody upfront is pushing on the brake. So, that's going to be that LED strip that comes on when we turn on our turn signal. If I check my blue wire, I'm getting a constant 12 volts here. That blue wire is going to be our left turn and brake signal.Now, we can go over to the right side and we're going to check for the right turn signal. Now, here on the passenger side, we're getting voltage and alternating voltage out of this blue wire with the black stripe, while we have our turn signal on. We're going to know that this blue wire is going to be for our right turn signal.Here we can see that LED strip, and the turn signal both coming on at the same time. But if I turn the turn signal off, and hit the brakes, we can see that only one of those lights are coming on.Now, this panel here, where our tail light wires are going to, we are going to need to pull that down. I'm going to take a plastic trim panel tool, come to the side of my panel here. I'm going to slowly and gently start pulling away, releasing some of the clips.Now, if we look right here, this upper section is right behind it. So it might help so slowly pull away and kind of push on that while you're pulling. Now that we have the side slightly loose, we're going to come to the center section right here. Now, yours may have this turn style knob, ours is actually missing the backing of it. But, once you get it loose, you're going to want to swing that cover out of the way. It's going to expose two torques bits. I'm going to be using a T25 torques bit socket to remove those.With those removed, you're going to want to take a trim panel tool, you're going to want to start working your way around the edges, releasing the clips as you go. There's going to be one right here, at the corner. We'll keep moving towards the center, loosening everything up. Then we can move over to the other side, now that this side is a little bit loose.We've come to the top section, where this panel meets the glass. Actually, I take my trim panel tool and I'm going to pry the panel away from the glass. And you're going to want to work your way across.Now, with the top section loose, you're going to want to pull straight down. Because there's a few clips holding this center section in place. I just want to be careful, because there are some electronics hooked to close and open the gate right here.Now, for the electronics here. It might be easiest to grab a inaudible 00:06:35 screwdriver, and push in on that tab right here. Once you have that tab pushed it, you just want to pull out on the connector so that we can put the panel aside for now. Right here, there is going to be small tab on the very end as well. Just push it in with a screw driver, then you can pull the connector out. We'll set the panel aside, so it won't get damaged.Now, what I like to do first is find the location of our module box, that way we know that our panel can go back in place and it's not going to interfere with anything. I've got a couple different options of how we're going to do it. We have a hole in the top, or we can either zip tie it to something. Or, we can take the double sided foam tape, and stick it the inside of a panel.I'm going to chose to use the double sided tape. We won't have to worry about finding something to zip tie it to. I'm going to take the backing off, push it on firmly, make sure it hears nicely. Then we take the other side of the backing off. We're going to be mounting ours, right here, in this little hole right here. You just want to put your box in, push against it firmly so it's not going to fall off. Making sure that the glue sticks.Now we can ready to start routing some of our own wires. We're going to have a white wire, with a ring terminal attached. That's going to be for our ground. Now, the ground, we do have an option of either finding a factory ground, that's on our tailgate here. Or we can take the provided self-tabbing screw, and screw it into some sheet metal. I'm actually going to go behind some wires, to help secure it a little bit.Then, I'm going to find a nice high spot, that I know is not going to interfere with anything. But, I also know that it's not going to go through to the outside. I'm just going to be attaching it right here, to the sheet metal.If you look on each one of our connecting wires, they're going to have the corresponding that they go to printed on the label here. We're going to go ahead and start with our tail light circuit. Which we're going to tap into on the drivers side.If you need to, you're going to want to cut away some of this protective coating around the wires. Because we are going to have to tap into not only the tail light, but also the turn signal over here as well. I'm just going to take a razor knife. You want to be extra careful, not to cut the wires, or yourself. But you're going to want to cut the sleeve back, enough so that you can gain access to the wires and have enough room to work with.Once you have a good portion peeled back, and you can access the wires individually, and have some rom to work, you want to go ahead and do that on the passenger side as well. Now, for this side, since it is for the tail lights, we figured out that our tail light is going to be our gray wire. So, we're going to want to open up our connector here. We're going to take our wire, and we're going to make sure that it sits nicely in between the channel here. Once it is, we can go ahead and take the cover, close it in place. And you want to make sure the arrow is pointing towards the tail lights.Once we have it in place, and we have it closed down, we're going to take the foam sticky tape here, we have, that come in our kid. You want to make sure that wire isn't moving around, and it isn't hopping around after you close the cover. Since ours was moving. I'm going to go ahead and double check to make sure that it didn't come out of that spot. It might help to put a little bit of pressure, so then that holds it in place.Once we have it locked into place, we're going to take that foam tape. We're going to wrap it around the connector, and the wire. Making sure that everything is nice and secure. And it's also going to help from any noise that may be caused, since it is plastic behind the panel here. It'll keep it from making any notice if this rattles.Now, we can move onto our left turn signal. Which is also, if you remember, going to be our brake signal. That one is going to the be the blue wire on the drivers side. We're going to do the same process. Give it a nice little tug, so I can get it to sit in there nicely. Then we can grab our foam tape, and wrap it around it.Since we are limited on space. I'm going to be my tape started on one side, rotate my connector. Making sure that everything is staying in place. Then wrap my foam around to the other side. You just want to try not to get any other wires, interfering with anything. You want to make sure that it's nice and locked in place. And that the tape isn't going to get in the way either. We just have our gray wire inside one connector, and our blue wire inside the other. While the other two wires are just hanging out.We should have two more connectors left. A right turn signal, and one that says stop. Since our turn signals and brake lights are the same circuit, and they work off the same light, we're not going to be connecting the stop light signal. So, we're just going to need to take the right turn, and we're going to need to take the rubber band off and wire it over to the right side of our car.We can go ahead and open it up. If we remember our right turn signal is going to be the blue wire, with the black stripe around it. Coming off our modules, we're going to have a black wire that's just a bare stripped wire at the end here. We're going to take the butt connector that comes in our kit, slide it over our wire. We're going to crimp it down.Now, on the other end of our butt connector, we're going to take the included length of power wire. And we're going to strip back the end of it and we're going to be attaching it to the other side of that butt connector. Now, we're going to need to run this wire up to the battery so we can get power for our module box.Now, our black wire, as I mentioned, is going to have to get to the battery. Fortunately for us, our batter is actually in the cargo area, towards the front. So, what I'm going to do, is I'm going to run my wire. I'm going to tie it along to some of the existing wiring up here, come down this panel. I'm going to come up and then sneak in, come down, and run it to the battery.So, first thing we're going to need to do is pull up this cover in the trunk. We're going to lift it up, fold it back. Then if we come to the back section here, and we lift up, we can pull the cover out. And we'll set it aside, that's where our battery is going to be.To help me get my wire from the open end of the panel here, to the back, I'm actually going to take a piece of airline tube, you can use whatever you have laying around. Even if it is just a coat hanger. I'm going to start feeding it through that panel there, until I can reach the back. Then, hopefully be able to just pop that panel lose in one area. Be able to fish it out.So, I fed my airline tube that panel. Then I just reached back here, popped it lose, so I could have it coming out back here. Now, I'm going to take that black wire coming off my module box. I'm actually going to feed it into my airline tube. inaudible 00:13:54 something to grab onto.Now, I can start feeding that airline tube through. And pulling the wire through. Just so I don't have to worry about damaging the wire, you might want to go ahead and pull that whole panel lose. Then we can actually just tuck it behind there, just want to watch out for all the clips. Make sure that the wire doesn't interfere with anything. I'm going to pull all the slack through.Now that we have our wire ran to the back of the panel, I'm going to go ahead and put a small loop in there. Then zip tie it to this piece here, which is actually holding all the rest of the wires. For one top, probably one right here at the bottom to make sure everything is nice and secure. Don't have to worry about that wire going in any direction we don't want it to go.For routing purposes, you're going to want to go ahead and pull everything out of the trunk, the spare, and the panels holding all the spare tools in place. Just to make it easier, so we don't have to fight everything to get it out. If we unscrew our spare, and grab this.There should be a small button right here, we can push on it. It should disconnect, then we can set this aside. Then underneath, we can unscrew the turn knob. Then we can pull our spare out, and set that aside as well.Now, with the spare out of the way, we're going to go ahead and come to the edge of the plastic trim piece. Then our threshold, you're going to want to pry up on the very corner here. I'm using a plastic trim panel tool. So, I don't have to worry about scratching the plastic. Once we have that section pried up, you're going want to keep pulling up, working your way across.We're going to go ahead and set this piece aside as well. If we come back to where our wire is routed to, we're going to start by grabbing the weather stripping. You're going to want to pull it away, going all the way up to where our wire is, and you're going to want to go all the way down, to where the threshold is.We just just set is aside, on the inside of the vehicle. Now we're going to want to tuck our wire in between the body panel, and interior panel, running it down towards the threshold. Now, once we get it to our threshold, we're going to go ahead and run it to the inside of the car. Underneath the carpet area here, we'll pull all the access wire towards the inside of our car.So, we can go ahead and put our weather stripping back in place. I just want to line it back up. Push it in until it sits nicely against the seal. Now, we take our wire, make sure you go in between the back body panel here, and this foam panel. I'm going to go underneath, and start pushing my wire through. Until I can grab it on the other side of this foam.Then you can grab the wire, and start pulling the excess out. Depending on where you want to route your wire, you can do that and then you can start sliding it over. Pull all your excess wire through. You'll want to take the end of your wire, if you come underneath the back part of this foam here towards the front of our car. You can actually go up, come out right by the battery here.So, we pull the excess slack out. What I like to do, is take my wire, making sure I leave myself enough slack, and tuck it underneath the outside edge of the foam here. That way my spare tire won't rub against it. I don't have to worry about anything like that. Just lift up slightly on that foam panel, and push the wire underneath.Go ahead and pull that cover off the positive post of our battery. Now we're going to need to estimate, about how much wire we're going to need. We go ahead and cut our black wire that we ran, and we strip back the end of it. We're going to take another one of our butt connectors, and we're going to crimp it onto the end of the black wire there.Now, on the other end of our butt connector, we're going to be attaching our fuse holder. Because our kit is fused protected. Now, it's already pre-striped. So, we can just take the end, put it into our butt connector, and crimp it down.Now, on the other end of our fuse holder here, we're going to grab the ring terminal, that they provide in our kit. We're going to slip it over the wire and crimp it in place. Now we're going to need to grab a 10 millimeter socket to remove that nut.Now, in our application the nut doesn't want to come off all the way. Rather than taking the chance of stripping it, I'm just going to take a pair of cutters, and I'm going to cut a small notch out of my ring terminal. That was I just take it and slide it right over the bolt. Then I can re-tighten that bolt up.Then we can put our 15 amp fuse in the fuse holder, start cleaning up our wires. Putting all the panels back in place. just going to take all my loose, excess wires. And I'm going to tie them to some existing wiring back here. I'm going to bundle them all up, right by my converter box, that way I know when I put the panel back, they won't be interfering. I just want to mention, when you are tying your wires up, you want to leave your four pole nice and loose, and hanging down because we're going to need to find a spot to route that, when we get done putting all the panels back in place.Just remember when you're putting your panel back in place, to plug the connectors back in. So the lift gate will work. Once we have those connectors in place, we actually come to the inside of the panel here. We're actually going to take our four pole flat, we're going to route it, just the inside of where that panel opens up. That's where we're going to be hiding our wire, is right in through there.If you open it up, your wire should be hanging out the bottom. That we know we can tuck it up in there, when we're not using it. You're going to want to align the clips up, and you start pushing it back into place. Start popping your panel back into place. Once you have motion the clips in place, we can put our screws back, underneath this panel.Let me put our spare back in place. Finally, we can put our covers back. Our final step is going to be learning the wiring system to the vehicle. You're going to want to start your care, then you're going to want to run each function, separately, for at least five seconds. I'm going to go ahead and turn my headlights on. So that my tail lights come on, we're going to wait a few seconds. We're going to turn those off.Now, we're going to hit our brakes, and hold on for about five seconds. And you want to let go, and you're going to want to turn your left turn signal on, turn it all the way off. Then turn your right turn signal on.That should run our car through our learn mode, so let's go back and test our wires. Now, to make sure everything is working properly. I'm going to plug in my four pole tester. If you need one of these, you can pick one up on our website using part number I26. I'm going to grab an extra set of hands, and they can run my lights. So I can make sure that everything is working. Can I have the headlights, please Looks good. Left turn signal. Good. Right turn signal Now the brakes. And brakes and both turn signals.With everything looking good, we're ready to hit the road. That will finish up our look at the Tekonsha ZCI Circuit Protective Vehicle Wiring Harness for a four pole flat trailer connector, and installation kit. Part number 119250KIT on our 2018 Audi Q5.

Questions and Comments about this Video

Steve O.

My 2018 SQ5 has the oe hitch and harness option. Can you tell me how to disable the rear proximity sensors when the harness is plugged in? I want to use the corresponding male plug for the oe socket and an aftermarket plug for the trailer end.

Etrailer Expert
Reply from Jon G.

Typically when a vehicle has the rear proximity sensors there is a way to disable them when towing a trailer. You might either have a tow mode that disables it or you might be able to do that manually. If you check out your owner's manual it should give you some insight into this.


Hi, what would I need to install a 7 pin harness in a 2018 Audi Q5? Is the installation much different than this kit?Thanks

Etrailer Expert
Reply from Heather A.

This installation kit is a 4-way trailer connector for the 2018 Audi Q5. If you need a 7 pin you will need to install this 4- way connector in conjunction with a 7-way kit part # ETBC7. The ETBC7 comes with the 7-way plug, duplex wire, hardware and circuit breakers needed to complete the installation on your 2018 Audi Q5. I have attached installation instructions below.

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