1. Custom Fit Vehicle Wiring
  2. Tekonsha
  3. Custom Fit
  4. Trailer Hitch Wiring
  5. 4 Flat
  6. Powered Converter
T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

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Custom Fit Vehicle Wiring

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Custom Fit Vehicle Wiring 118578 - 4 Flat - Tekonsha
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Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system. Call 800-298-8924 to order Tekonsha custom fit vehicle wiring part number 118578 or order online at etrailer.com. Free expert support on all Tekonsha products. Guaranteed Lowest Price and Fastest Shipping for T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector. Custom Fit Vehicle Wiring reviews from real customers.
  • All Info
  • Reviews (366)
  • Q & A (146)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring

  • Custom Fit
  • Trailer Hitch Wiring
  • Tekonsha
  • 4 Flat
  • Powered Converter

Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system.


Features:

  • Provides a 4-way flat trailer connector at the back of your vehicle to power your trailer's signal lights
    • Compatible with 5-pole, 6-pole and 7-pole adapters (sold separately)
  • Connects quickly and easily
    • Locate connection points in trunk
    • Plug in T-connector
    • Run hot lead to car battery
  • Includes ModuLite to ensure that your vehicle's wiring matches that of your trailer
    • Powered module connects directly to battery to avoid overloading vehicle's electrical system
  • Constructed of 16-gauge bonded wire
  • Comes with dust cap for 4-way flat connector


Specs:

  • Maximum amperage:
    • Stop/turn lights: 5 amps per circuit
    • Tail lights: 7.5 amps per circuit
  • 1-Year limited warranty


Installation

This custom-fit T-One connector plugs into your vehicle's wiring harness, which is located inside your trunk, behind the tail lights on both the driver's side and passenger's side. You will need to remove some interior trim or carpeting to access the harness. Once you've plugged in the T-connector, run the hot lead up to your car battery. Connect the lead to the included fuse holder, and then connect the fuse holder to the positive terminal on your battery and insert the provided fuse.


Once installation is complete, the 4-way flat connector will be stowed in an out-of-the-way location within your trunk.


It is recommended that you use a small amount of grease on all electrical connections - the plugs on your automobile and the 4-pole connector itself - to help prevent corrosion.


ModuLite Powered Tail Light Converter

A ModuLite power module is built into this T-One connector. Because most trailers run on a two-wire system - wherein the brake and turn signals are carried on one wire - the separate brake and turn signals from your vehicle's three-wire system need to be combined so they are compatible with the wiring system of your trailer. This power module functions as a tail light converter to combine the brake and turn signal functions of your automobile so that they run on one wire to properly activate your trailer's tail lights. Note: This will not affect how the tail lights on your vehicle operate.


With a ModuLite, your trailer's lights will be powered without overloading your vehicle's electrical system. Because the module draws power directly from your car's battery and bypasses the electrical routes that are used by a basic wiring harness, there is virtually no draw on your tail light circuits.



118578 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

Item # 118578

Installation Details 118578 Installation instructions

This Product Fits The Following Vehicles



California residents: click here



Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118578

Average Customer Rating:  4.8 out of 5 stars   (366 Customer Reviews)

Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system.

- 118578
by:
2018 Toyota RAV4

Easy to install. Came with all the parts and instructions. Video on eTrailer website was super helpful! 682884


Comments
Great! No issues with the hitch. Just dragged a UHaul trailer to Florida from Maryland - through lots of rain. Now that I have a hitch Im thinking of getting one of those things to carry more stuff instead of a car topper.
Mitchell - 08/10/2020

96882
Comments
Havent used it for about a year, but still installed and working perfectly!. Just used it for a UHaul again.
Mitchell - 08/10/2020

96883

- 118578
by:

Installation is not near as easy as they make it look in the video. Be prepared to spend some time on this getting the connections released from the factory connecter will really wear your patience 735370



- 118578
by:

The materials and instructions are sound. I installed it myself. My advice is that if you don’t own a torque wrench and don’t have thick hide then hire somebody else to do this for you. Not worth the struggle. 645282



- 118578
by:
2015 Toyota RAV4

This wiring kit was everything they said that it was. Plugged right in (when I finally got to the harness) and it works great. I didn't like leaving the flat 4 connector stored inside, so I ran it down through a rubber plug that was already there so that it is out where I need it all the time. Thanks. 430821


Comments
I have used it a lot and it is working perfect.
Steve - 09/10/2018

43418

- 118578
by:
2013 Toyota RAV4

If you're comfortable pulling panels and routing wires, install is a snap. It is a plug and play solution that removes the need for custom wiring and works perfectly. 613639



- 118578
by:
2015 Toyota RAV4

The best part is that it connects into the existing lighting system with electrical T-connectors. The worst part for me was running the power wire underneath the vehicle up to the battery. Other than that everything went perfectly, and the video on the website was extremely helpful. I'm a novice, and it took me about 2 hours to complete the job from start to finish. 573950



- 118578
by:
2015 Toyota RAV4

The 76134 receiver is well made. All weld beads are continuous and consistent and the material is sized right for adequate strength and minimum weight. Mounting bolt hole pattern is right on. Paint is good and consistent with no dings or scratches. Installation was straight forward. It was necessary to procure a M12 X 1.25 tap to run through the mounting weld nuts in the frame in order to get the bolts to thread in; not a fault of the receiver but the effects of four years of over the road use of the 2015 RAV4. Also the small amount of extra money for this hidden crossbar version of a receiver was worth it when looking at the final installation. The 118578 T-One harness kit installation was also straight forward and it works as it should. Installation was made a little less difficult with the use of the ALL648544 trim pad remover that was purchased with this order. 647642



- 118578
by:

I selected this unit because e-trailer has such a good video about installing one. However I found in real life that the video missed several good hints, and became quite vague when it came to the more difficult steps. But that is also true for the printed instructions that come with the kit. First, go spend the ten bucks at your local auto store for a good tool to pop out the panel fasteners. 1. On the " right side the tail light connectors, the "catch" that holds the connectors together is hidden. To see how they work, check the matching connectors on your unit. 2. The wire bundle between the right and left side is too short. There is no flat area on the right side large enough to mount the control module. I just wrapped the control module in some foam, taped it with duct tape, and left it loose (but still behind the left rear panel) . 3. Getting under my vehicle to route the power wire on a creeper is impossible. But the instructions offered the alternate of running it inside the body. So that's what I did. BUT, getting it through the bulkhead turned out to be a major problem. (I, and my son, spent most of an afternoon just on that item alone.) Seriously think about whether you have the the ability to do this job before you purchase. These problems are not unique to this brand, and you will run into these same problems regardless which unit you buy. 131043



- 118578
by:
2016 Toyota RAV4

For many years, I've installed my own trailer wiring with a test probe and scotch connectors. I was going to re-use one of my old "passive" harnesses but my mechanic warned me that newer cars are more sensitive to the current load and I should use a "powered" unit made specifically for my 2016 Rav4. That led me to the 118578 T-One wiring harness. I won't say installation was a breeze, but the T connectors certainly simplify the job. The included instructions are not the greatest, but etrailer's video is very helpful in showing which interior panels to remove, and how to do it. It's tight quarters, but by starting on the drivers side, you can see how the factory plugs disconnect. When you get to the passenger side, the plug will be facing away from you and is really hard to disconnect, even when you know how it works. What I eventually did was to detach the plug from the pillar so I could turn it around and get better access. This part of the installation, and attaching the ground went fairly easily, The time consuming part is running the hot lead to the battery. The instructions say to run it under the car. That would be fairly straightforward, but I'm not comfortable with that. It's probably fine, but I live on dirt roads and the underside is prone to bottoming out in mud and snow. I read of folks running the wire inside the car, so that's the route I took. Getting the wire to the front was simple....certainly no more difficult than jacking the vehicle and laying under it. I was able to thread the wire under the side panels in the back. The door sills pull up easily by hand, and then you can push the wire through the door post covers. The hard part was getting through the firewall. The wiring bundle for the entire car runs through one hole under the dash on the drivers side. There is one huge rubber grommet and the bundle runs through the center. There is a hole in the side of the grommet that looks like it was made to accept an extra wire, but it has to be punctured for the wire to pass through. When the wire comes out the other side in the engine compartment, it's in a totally inaccessible (and barely visible) spot. I had to make a lot of attempts before the end of the wire finally protruded somewhere I could grab it. After that, connecting to the battery was simple. Now that it's done, I'm glad I installed the battery wire inside. I have yet to pull my trailer with this kit, so I can't speak to reliability. As for the installation, this kit made installation as easy as it can get. 400826



- 118578
by:
2017 Toyota RAV4

Really heavy duty, weighs almost 40 pounds. Instaltion a snap (watched the video a bunch of times first). Took less than 45 minutes and that is including time needed to get all tools ready. A online hint of using the box it came in to support it while attaching it to the frame was extremely helpful! Fit perfectly, looks great. Now I'm ready to attempt the wiring harness. Have seen the videos but wish they had one without the battery in the trunk. I foresee the hardest part finding a way to get the hot wire to the battery under the hood. 374607


Comments
Haven’t used for towing yet.
Bobbobs - 04/26/2018

37750

- 118578
by:
2017 Toyota RAV4

I think that the product overall is good. But, I don't think putting this Assy. together is for novices. The video was helpful but, I improved on the safety and more professional installation. One thing I have a problem with is running the hot wire over the sub frame of the car. This is how the video shows the installation. The first time you go to your tire dealer for tires he probably will place his lift support guess where? On top of the hot wire you ran over the sub frame. Guess what happens then - Electrical short! I drilled an additional hole (in the sub frame) and then ran the wire through a piece of rubber hose for protection. Also, an electrical plug mount is welded on the hitch. Why not use it rather than slamming your trunk on the plug wire? Such an armature set up. 545604


Comments
It is working out fine. I only use my Rav 4 for pulling small light trailer. I think that my pictures show a quality professional job. I was a machinist for many years and can make custom parts that I needed.
John D - 07/24/2019

58164

- 118578
by:
2003 Infiniti FX45

Installation of the hitch was fairly easy. I used the box as my assistant to hold up the hitch while I bolted it on. As others have stated the holes don't line up perfectly from side to side but with a bit of maneuvering I was able to get the bolts in. Installing the light wiring kit was a bit harder. Removing and reinstalling the panels was easier than I expected. (Although I got a few cuts and my hands and arms) The hardest part was running the wire up front to the battery. As I don't have a car lift in my garage getting under the vehicle was challenging. I did jack up one side and that helped. I went up the center and followed other wiring. I was able to route the tail through the jack storage box and it makes a good storage place for the cable as well. The best part was saving about $200 over a business install and about $800 over a dealer install. 243262



- 118578
by:
2017 Toyota RAV4

Installed in a 2017 RAV4 by a (as defined by the government) elderly person (over 65). The good: Almost everything necessary comes in the box (extras obtained at another store); all connectors snapped together as they should; and all panels/trim pieces came loose without breaking, then popped back into place so one cannot tell they were ever apart. The bad: Those extra parts needed (probably my fault as I installed inside as suggested by another reviewer rather than underneath) The ugly: My hands (one looks like I've been attacked by a small animal) and arms will take several days to recover from being scraped and stabbed by the rear side panels (there was some blood to be wiped off one) and their retaining pins and it took 3 half days to complete (some of that spent "pondering" and taking that trip to another store). First, I appreciate the video posted by etrailer showing the installation. I do however wish a little more time was spent on making the connections behind the panels in the back. (Reminded me a bit of my high school geometry class where the proof was left to the student.) Second, I spent some time "pondering" whether to do an outside hot wire run from the back up to the battery or inside, under the trim panels on the passenger side and through the firewall. In the old days there would have been plenty of places to zip tie this wire along the outside underneath. However, with all of the plastic panels (I'm told for aerodynamics), without taking them down, I didn't really see a clear path from back to front. Other reviewers have posted about the ease of running the wire down the inside on the passenger side - only removing a couple of trim pieces necessary - with the hardest part getting through the firewall. I elected the inside routing once I figured out how to get through the firewall (see "fourth", below). Third, at this point, I pulled the back cargo area apart, i.e., took out the jack, the across the rear panel, the two rearmost side bottom black panels, and the panel in front of the spare. (not necessary to take out the spare) This gave me some idea of what I'd be dealing with once I got the hot wire routed. Fourth, I took off the quarter round trim at the side of the passenger foot well (just pops off), the trim behind the glove box (a couple of little tabs near the glove box hinge & it drops down - retained by those tabs and a couple of protrusions, one at the firewall and one at the right), and the side "kick" panel at the side of the passenger footwell (pops off after removing a square plastic coated nut, about the middle of the panel). After some pondering and looking around I discovered a large rubber boot in the firewall behind electrical junction boxes on the outside passenger footwell. It is hidden underneath insulation so look for where the large cable bundle and what is, I think, a fluid hose for the rear wiper, penetrate the firewall. On the engine side, this boot is behind the shock tower. You can sorta see it but most of the work was by feel. This boot has a thin rubber nipple protruding on the engine side, on the fender side of the boot. I cut the end off this nipple with a small pair of side-cutters. I then fed the wire through that nipple from the engine side. Takes some pushing but it will come through on the inside. I then routed the wire along the engine side of the firewall, then along the driver side fender to the battery. Once I had sufficient wire in the engine compartment, I pulled the excess into the passenger footwell. (Be sure to leave enough in the engine compartment so you can zip tie it out of the way. Installer's choice as far as routing. There are plenty of cables to zip tie to.) Fifth, the relatively easy part of getting the wire to the back. I did find an old wire shirt hanger in the closet which I cut up to use to fish the wire through the wire race behind the plastic at the door pillar. The quarter round plastic in the back seat popped off easily. I then stuffed the wire in the small gap between the rear forward plastic trim piece and the carpet, did the same in the rear compartment, then routed through the metal "tunnel"/beam in the very rear to get it to the passenger side to hook to the black wire in the harness. This is where I spliced in about 1.5 feet of automotive wire from another store with the butt-splice connectors (the red ones work just fine), also from another store. Sixth, the rear cargo compartment side panels come loose pretty much as shown in the video. As the trim retainers let go with quite a pop/snap it is a bit disconcerting as it sounds like something is breaking. The real downside is, while the wire connector is exactly where it is shown to be in the video, it is very difficult to lay hands/fingers on. Getting those connectors to come apart was the hardest, most difficult part of the job, although after the fact, looking at them, they should have easily come apart. I was finally able to use a long, flat-blade screwdriver to pry them loose from the metal panel. Once I'd done that getting them apart and the appropriate limb of the towing harness "spliced in" was literally a snap. The connectors only go together one way and, if you'd broken one of the retainers when you pried it loose with the screwdriver, there is the same connector with the same retainer on the harness limb. Seventh, mounted the controller box to the outside (sorta facing the spare tire at about a 45 degree to the forward/aft vehicle centerline) of that open box beam which runs across the back. Used the mounting tape and a screw. Also, when mounting the grounding wire, I did use my Dremel with a little grinding wheel to get to bare metal under the end loop. Figured it couldn't hurt to get as good of a ground as I could. I also piloted the screws even though they were self tapping as i thought it would just made things easier. Eighth, made the connection of the hot wire to the battery. This bit was straight forward and went exactly as the instructions/video said it would. Yes, I left the fuse out until ALL connections made. Ninth, I'd seen a tester for a flat trailer connecter at another store. Bought for, as I recall, $3.99. Used it to test the connector before I buttoned everything back up. Tested all good. Final comments: Actually not all that hard, just a lot of "pondering", working blind, and some poking and scraping of the hide. The extras cost me, probably $10 - $12. I'd recommend a crimping tool/wire stripper tool if you don't have one, also available at another store for around $5. (I had two so did not need another.) After watching the video, I thought I could do it, bought the part, then just kept plugging away at it. 473348


Comments
Used the set-up to plug in a Thule Transporter Combi for a trip from SE AZ cross country to the Boston area in April 2017. Worked just fine but have not used it since. Transporter is hung from the garage ceiling waiting for the next adventure.
SteveO - 01/05/2019

48254

- 118578
by:
2013 Toyota RAV4

I would give 5 stars but because of the model I drive, the work involved is more that I though was needed. No fault of the harness. Works great! 898914



- 118578
by:
2017 Toyota RAV4

Easy to install, components seem to be high quality, bright lights, big city!!! 893210



- 118578
by:

Still sitting great, very happy with this product 887070



- 118578
by: 09/19/2020

Easy to install! My only suggestion is that where the fuse is placed that a label or visible imprint stating both the amperage rating and type be listed! Another idea for the manufacturer would be to mould a separate storage case to hold a spare fuze and and extra space to pull and store the working fuze while working on the trailer. That way you will not lose the working spare and when travelling have an emergency spare! 883541



- 118578
by:

Easy plug and play wiring harness. 883172



- 118578
by:

super easy. watch the video and become a professional 880706



- 118578
by:

I love my trailer hitch. Everything is exactly right. The only issue we have had is that there seems to be a burr on the hole that the securing pins go through and it has gouged the pins. We need to get a diamond grinder and grind it down, but other than that, it has been great. 880660



- 118578
by: 09/04/2020

Worked perfectly. Step by step installation video spot on. 874015



- 118578
by:

Works well Did not like to have to run hot wire from battery 869245



- 118578
by:

This kit was very simple to install. The videos explain everything perfectly. If you're not sure this is what you need, the customer service team will help you get set. 867640



- 118578
by:

867480



- 118578
by:

very good product 866915


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Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

  • Parts Needed to Add 7-Way Wiring Harness to 2013 Toyota RAV4
    The part you had asked about is no longer in production, but thankfully we do have a fantastic option that will allow you to install a 7-way on your 2013 Toyota RAV4. For the easiest install I recommend starting with the T-One Vehicle Wiring Harness with 4-Pole Flat # 118578, which does not require splicing into your Toyota's wiring, just plugging into connection points in your trunk and running a hot lead to your battery, as you can see in the linked installation video I added of this...
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  • Fuse Blows on T-One Wiring Harness When Hooked Up to a Trailer
    This sounds like you may have a pinched wire. Look at the green, yellow, and brown wires that are ran through your vehicle and check for any areas where the wires are pinched and touching the metal of your vehicle. If they are, this will cause the wire to be grounded out, which in turn will cause them to short. Replace the fuses and test each function without the trailer hooked up. Use your right blinker to see if it's the green wire. Use your left blinker to see if it's the yellow...
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  • Will the T-One Vehicle Wiring Harness 118578 Fit a 2018 Toyota RAV4 Hybrid
    The T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector part # 118578 is a fit and an excellent option for Hybrid models of the 2018 Toyota RAV4. In regards to installation, this will actually be a bit easier since you don't have to run the power wire up to the engine as this is usually in the rear cargo bay instead.
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  • What Size Fuse Goes in Fuse Holder of Trailer Wiring Kit for 2016 Toyota RAV4
    The fuse that installs in the yellow fuse holder of the Tekonsha trailer wiring kit part # 118578 that you referenced for your 2016 Toyota RAV4 is 15 amp. I attached an install video for this kit on a similar RAV4 as yours for you to check out as well.
    view full answer...
  • Does T-One Wiring Harness Need Power For Trailer Lights To Function
    Your 2014 RAV4 has what is called separate wiring which means the brake and turn signals are run on different wires. A trailer runs on a 2-wire system where the brake and turn signals are on one wire. The module that is included with the # 118578 wiring harness takes the separate signals from the vehicle and combines them so they will work with the trailer wiring. It does not affect how the light work on the vehicle. The converter has a hot lead wire that needs to be connected to the...
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  • Can Power Wire of 2018 Toyota RAV4 Hybrid be Ran to Rear Battery
    Yes, when you install the Tekonsha trailer wiring kit part # 118578 on your 2018 Toyota RAV4 Hybrid you can run the power wire to the battery in the rear of the vehicle which would be easier than running to the front of the vehicle.
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  • Recommended Wiring Kit for Towing with a 2017 Toyota RAV4
    Out of the Curt # C56350, Tekonsha T-One # 118578, and Hopkins # HM11141820 wiring harness kits for your 2017 Toyota RAV4 Hybrid I highly recommend going with the T-One option. The reason being that we have found the Tekonsha electronic equipment to last longer and work better than many other brands. The installation is fairly simple and only requires you to plug in the T adapters behind the tail lights, grounding a wire, and then run a hot lead up to the battery. I have attached a...
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  • Parts Needed to Install 7-Way Wiring Harness on 2015 Toyota RAV4
    The Draw Tite hitch part # 75235 that you are interested in for your 2015 Toyota RAV4 is a great choice for a trailer hitch. I attached an install video for it as well. For wiring you would need the part # 118578 to give you a 4-way and then would need the part # 37185 to convert it to a 7-way. From there you would need to run a 10 gauge wire like part # 10-1-1 up to the positive post of the battery through a circuit breaker like part # 9510. Since you wanted to do some towing you...
    view full answer...
  • Trailer Wiring Recommendation for 2018 Toyota RAV4 Hybrid
    Yes, we do have trailer wiring that fits your 2018 Toyota RAV4 hybrid. For that I recommend the Tekonsha kit part # 118578 because it installs without requiring any hardwiring and because it has the most reliable converter box of all of the kits we offer. I attached an install video for this for you to check out as well.
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  • Brake Controller and Wiring Recommendation for 2015 Toyota RAV4
    For installing wiring and a brake controller in your 2015 Toyota RAV4 you will need to start with a 4-way (if you do not have one). For that you would want the # 118578. I attachd an install video for this for you to check out as well. From there you would need to convert the 4-way to a 7-way so that you can install the brake controller. For that you will want the Brake Controller Install Kit and 7-Way Adapter part # ETBC7. I attached installation instructions and an install video for...
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  • Does Wiring Harness # 118252 Fit 2017 Toyota Rav4 LE?
    The T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118578 is the confirmed fit for the 2017 Toyota RAV4. This custom-fit T-One connector plugs into your Toyota RAV4's wiring harness, which is located inside your trunk, behind the tail lights on both the driver's side and passenger's side. You will need to remove some interior trim or carpeting to access the harness. Once you've plugged in the T-connector, run the hot lead up to your car battery. Connect the lead to...
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  • How to Route Power Wire from T-One to Battery on a 2018 Toyota RAV4
    The best route to run wiring from the back to the front of a vehicle, like the T-One # 118578 on your 2018 Toyota RAV4, is to keep it away from moving parts and run it through the frame when possible for best protection. We actually have an installation video of this being done on a 2018 RAV4 for you to check out. You can mount it in the cargo area if you would like or you can try to find a grommet in the cargo area of your RAV4 and route the 4-Way connector through it so that you can...
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  • Recommended Trailer Wiring Harness For 2017 Toyota RAV4
    For your 2017 Toyota RAV4, I recommend the Tekonsha T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118578. This custom-fit T-One connector plugs into your Toyota RAV4's wiring harness, which is located inside your trunk, behind the tail lights on both the driver's side and passenger's side. You will need to remove some interior trim or carpeting to access the harness. Once you've plugged in the T-connector, run the hot lead up to your car battery. Connect the lead...
    view full answer...
  • 2016 RAV4 Hybrid Trailer Wiring Harness Fit
    Tow Ready has confirmed for us that their trailer wiring harness # 118578 will fit and would work well. I attached a picture that points out which terminal to use on the battery for running the power wier of the harness. I attached an install video for you to check out as well.
    view full answer...
  • Recommended Trailer Wiring Harness for 2017 Toyota RAV4
    It sounds like you might be looking for a trailer wiring harness for your 2017 Toyota RAV4. For this, I recommend the Tekonsha T-One Vehicle Wiring Harness # 118578. This harness is custom-fit for your RAV4 and will connect directly to the built-in ports behind the trim panels in the cargo area of your vehicle. Once installed, this will give you a 4-Way connector at the rear of the RAV4 to connect with and power your trailer's signal lights. I have attached the written installation details...
    view full answer...
  • Vehicle Wiring Harness With 4-Pole Flat For RAV4 Hybrid
    I reached out to my contact at Tekonsha and they confirmed that the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118578 will fit the 2018 Toyota RAV4 Hybrid. The complete install video on the 2018 Toyota RAV4 is attached to this page.
    view full answer...
  • Does Power Wire of Trailer Wiring for 2018 Toyota RAV4 Drain Battery When Not in Use
    Since the wire to the battery does not draw any amperage when the vehicle is off and a trailer is not connected it would not drain it. It's the same principle as the wiring of your vehicle that already runs to the battery. When those circuits aren't active it does not drain it at all.
    view full answer...
  • Does the Power Wire of the Tow Ready 4-Way Harness # 118578 Have to Run to Vehicle Battery
    If you were to run the power wire of the Tow Ready Custom Fit Vehicle Wiring # 118578 to anywhere but the positive post of your vehicle battery you would void the warranty of the harness and could potentially damage the wiring of your RAV4 in the event of a short on the trailer wiring. The purpose of the battery wire being run to the battery is so that it bypasses the delicate vehicle wiring and eliminates the potential threat of the trailer wiring damaging the vehicle's wiring. It draws...
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  • Does Battery Need to be Disconnected to Install Tow Ready Trailer Wiring on a 2015 Toyota RAV4
    Step 11 of the trailer wiring harness part # 118578 that you referenced indicates that you have to disconnect the negative post of your vehicle's battery temporarily. You would lose some radio presets doing this but nothing permanent would get damaged. On the other hand, if you were to leave the battery connected there is a chance you COULD damage the electric system or get shocked yourself. I attached an install video for you to check out as well.
    view full answer...
  • Why Is Separate 12V Battery Power Connection Required for Wiring Harness 118578
    Thank you for your purchase of Tekonsha 4-pole wiring harness # 118578 for your 2016 Toyota RAV4. You ask a reasonable question about the installation of this item. It is not recommended to use a vehicle's auxiliary 12V power outlet to power a trailer wiring harness like Tekonsha # 118578. The reason is that doing so takes away the main advantage of using a powered converter, which is to isolate and protect the vehicle's wiring from any potential damage from a short or other fault on...
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  • My 2014 Toyota RAV4 T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
    To determine if the problem is on the 2014 Toyota RAV4 or on the trailer there are some tests you can do. First, disconnect the trailer for the RAV4. Then use a circuit tester such as # 40376 to test the vehicle side connector while someone sits in the vehicle and operates the light functions. If you do not get power on the connector while testing then the issue is on the vehicle side. Make sure that the harness white ground wire is attached to a clean metal surface. No paint or coating...
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  • Installing Power Wire for Tekonsha T-One Harness # 118578 on 2018 Toyota RAV4 Hybrid
    I spoke with my contact at Tekonsha regarding the T-One Vehicle Wiring Harness # 118578 (which is confirmed to fit your Hybrid model RAV4). He said that you will definitely want to connect the power wire to the positive post of the battery at the back of your vehicle. There aren't any specific or alternative instructions with regards to this process but you just want to route the wire back, making sure to avoid any hot areas or spots where the wire might get pinched. You will need to remove...
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  • Recommended Trailer Wiring Harness for 2018 Toyota RAV4
    For your 2018 Toyota RAV4 I recommend the Tekonsha T-One Vehicle Wiring Harness # 118578. This custom harness will plug right into factory ports behind the trim panels in the cargo area of your RAV4 to provide you with a 4-Way connector to power a trailer's basic signal lights. I recommend this particular harness because it features a higher maximum amperage for its circuits than the alternatives. We also get far fewer troubleshooting questions regarding Tekonsha harnesses than we do with...
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  • Where to Connect Power Wire of Tow Ready 118578 Trailer Wiring Harness on 2016 Toyota RAV4 Hybrid
    The terminal you have the power wire connected to looks like it's a fused terminal. I'd recommend connecting to the bolt that's closest to the positive battery post as shown in the photo I've edited for you. This will provide you with a direct connection to the battery. Tow Ready confirms that the # 118578 is compatible with your 2016 Toyota RAV4 Hybrid.
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  • 4-Way Trailer Wiring Harness Recommendation for 2017 Toyota RAV4
    Since your trailer does not have brakes and only weighs 1,000 lbs the type of trailer wiring kit you'd need would be a 4-way harness. Basically the 4-way is for just providing the taillight circuits to the trailer. For that the best option is the Tekonsha kit part # 118578 which is a confirmed custom-fit. I attached an install video for more info as well. The Tekonsha brand of trailer wiring is the most reliable option we have so it's the one we recommend the highest.
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  • Best Trailer Wiring Harness for 2018 Toyota RAV4
    The wiring harness I recommend for your 2018 Toyota RAV4 is the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118578 because it is easy to install on your RAV4; you will only need to plug it into connection points in your rear cargo area and run a hot lead to your battery. Additionally, you can have faith in how dependable this harness is because its manufacturer, Tekonsha, has a very strong reputation for creating quality wiring products. As such, this harness also...
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  • Correct 4-Pole Wiring Harness for 2014 Toyota RAV4
    To add a 4-way connector to your 2014 Toyota RAV4 I recommend the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118578. This is a plug-in harness so you can avoid splicing; I've added a link to an install of this harness on a '14 RAV4 as well as a link to a video review of the harness for you to take a look at.
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  • Wiring Harness 118578 Installation in 2016 Toyota RAV4
    In most modern trailer and vehicle wiring the ground wire color used is typically white. This is indeed true for installing the Tekonsha 4-pole wiring harness # 118578 in your RAV4. Often this white ground wire will have a ring terminal which can help us sort out its function. The black 12V power wire does indeed connect to the battery + terminal through the included fuse holder. For reference, I linked the written instructions and a video showing this wiring kit installed in a 2018...
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  • Trailer Wiring Harness for a 2016 Toyota RAV4 with LED Tail Lights
    All you will need is the proper wiring harness for your 2016 Toyota RAV4 and it will work just fine with the vehicle's LED tail lights. Trailer wiring harness # 118578 is a great option. I have included a link to a video showing an example installation for you.
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  • Hot Lead Wiring, Fuse, and Fuse Holder to Complete Trailer Wiring Harness for 2011 Jeep Liberty
    We have exactly what you need! For the black wiring that goes to the battery on your 2011 Jeep Liberty (12 gauge) and the required 10 amp fuse and fuse holder, all you need is the Modulite Installation Wiring Kit # 118151. This kit includes the those components along with 8 cable ties, a couple of ring terminals and a butt connector for installation.
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Info for this part was:

Expert Research:
Mike L
Expert Research:
Michael H
Expert Research:
Jameson C
Expert Research:
Adam R
Expert Research:
Jeffrey L
Video Edited:
Joshua S
Video Edited:
Jacob T
Video Edited:
Dustin K
Video Edited:
Chris R
Test Fit:
Nicholas E
Test Fit:
Randy B
Test Fit:
Brent H
Test Fit:
David F
Video by:
Kathleen M
Updated by:
Laura H
Updated by:
Sarah W
Updated by:
Alexander C
Updated by:
Isabelle B
Installed by:
Cole B

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