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

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

Item # 118505
Our Price: $65.71
You Save: 35%
Custom Fit Vehicle Wiring

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Custom Fit 118505
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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 - no cutting, splicing or tapping required. Powered ModuLite reduces strain on wiring system. 1-636-306-4830 to order Tekonsha custom fit vehicle wiring part number 118505 or order online at Free expert support on all Tekonsha products. Great prices and Fastest Shipping for T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector. Custom Fit Vehicle Wiring reviews from real customers.
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  • Reviews (136)
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  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118505

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

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 - no cutting, splicing or tapping required. Powered ModuLite reduces strain on wiring system.


  • 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 - no cutting or splicing of wires
    • 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


  • Maximum amperage:
    • Stop/turn lights: 2.1 amps per circuit
    • Tail lights: 5.6 amps per circuit
  • 1-Year limited warranty


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 wire with the fuse holder to your car battery and connect it to the positive terminal. Then insert the provided fuse into the in-line fuse holder.

Once installation is complete, the 4-way flat connector will be stowed within the spare tire compartment of 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.

118505 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

Installation Details 118505 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Satisfaction Score:

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118505

Average Customer Rating:  4.9 out of 5 stars   (136 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 - no cutting, splicing or tapping required. Powered ModuLite reduces strain on wiring system.


Order arrived as specified, and was exactly as described! I am very impressed with how well designed and constructed to be an "exact fit" for our 2015 Toyota Prius! I ran into some difficulty and wound up removing the rear bumper skin to install 2 nuts inside the frame of the vehicle because the vehicle had been in an accident, and apparently the body shop facility that repaired the car (prior to our ownership) neglected to replace the weldnuts!
It was still an easy install, just required a little more time, and effort due to no fault of ETrailer or the manufacturer of the hitch.
The wiring harness setup that ordered greatly simplified the light hookups, and was great quality! Exactly as described!
I would definitely order again, and I highly recommend ETrailer, and their products!

2015 Toyota Prius

I watched the installation video twice and then installed my wiring harness to my 2010 Toyota Prius in 15 minutes. There was no two-faced tape for the power brick but there was a hole in the plastic casing for screwing it to a side panel. I probably spent 5 minutes finding a metal screw in my it was really about as 10 minute job. I purchased my hitch mount, hitch ball, and wiring harness from and everything fit perfectly, works perfectly, and I could not be happier with the products.

2015 Toyota Prius

I received my plug-in harness for my 2015 Prius. The quality is excellent and it went in without a hitch. Very impressed not having to cut, solder or shrink wrap. That is a big plus not dealing with those situations.


Really perfect the last year - not one hitch!


Works great! Great Quality and really benefitted from the installation videos.


Such clear directions for easy self installation; worked great on first try


super easy to install. All the parts went together and work perfectly.
Keep up the good work and I will, as I always do, use for my needs

2015 Toyota Prius

The harness was easy to install after watching an Etrailer video on Youtube.


Works well in my 2015 Prius. The package did not include a piece of double-stick tape as indicated in the instructions. Installation took about 45 minutes.

I am happy to hear that the harness is working well for you. We can definitely send that missing tape to you or it is perfectly fine to use any double sided tape that you have in the house.
-- Etrailer Expert Jenny N - 06/13/2022


Very easy to install and the directions were super easy to follow. A quality product that performs very well. I would absolutely recommend this kit.


These wiring systems that are car-specific are great. Super easy to install. Literally under 15 minutes.

2013 Toyota Prius

Have not yet got them installed but it looks like a high quality product and great shipping


I have purchased two items from etrailer in the last year or so. I am extremely pleased with both items. Both items arrived on time with instructions I could easily read and understand. I installed them myself with no trouble at all. etrailer is now my first choice when I need parts!!!


Not a bad deal! Everything was easy to install and I saved 170.00 by doing it myself.

2015 Toyota Prius

Your pics were right on! It took about 15 to 20 minutes to hook up/install. Worked like a dream on my 1959 Elgin /JC Higgins tent trailer. 2008 Prius. Thanks again!


Easy to install and arrived earlier than estimated. Will order here again!

2010 Toyota Prius

Easy install went quickly everything fit perfectly. Would buy again.

Toyota Prius

Because the taillights on my Prius run on low wattage LED bulbs, I couldn't just tap into the existing wires to run my trailer lights. I researched what would work and was happy to find the best solution was the wiring harness sold by etrailer. They work great.

After a year of use the wiring harness still works great.
Chuck W - 09/30/2015

2012 Toyota Prius

The wiring package instructions were easy to follow and the harness was the correct length to attach each connection. I am still using it today with no issues. I would recommend this to anyone with medium or higher skill abilities working on automobiles . Great product !!!!!!


Still performing perfectly !!!!!
Steve S - 06/13/2017

2005 Toyota Prius

The light wiring was easy to install, even for a non-car person like myself. The hitch went on, was a little tougher but that was because it was a bit heavier but I managed it by myself (and a floor jack). In all this was a great purchace and would recommend them for all your hitch/wiring needs. This reciever hitch and wiring went on a Toyota Prius.

Has anyone successfully installed this on a 2013 Prius. I have a 2013 Prius III.Thanks
-- comment by: Dave C - 04/25/2013

2005 Toyota Prius

Shipping was quick. I ordered a hitch and harness to get free shipping. I'm not very mechanically inclined, but installing the harness was pretty easy, once I got the grounding wire screw to bite (had to screw my body into position first).

Having used the trailer wiring and hitch a few times over the past year, I am quite satisfied with both. In the installation of the wiring, I was unprepared in that the process messed with my electronic door locks and I had to get them reprogrammed. Otherwise, no problems.Thanks again!
J S - 06/27/2014

by: 02/02/2022

Got products super fast, and the staff was very knowledgeable about products so could help me pick out what I needed.

2004 Toyota Prius

The product is excellent. I had a tow-bar outfit put it in as I'm too old to do that myself, but I did put in the wiring harness without trouble.

Just fine
Steve T - 09/29/2017

2010 Toyota Prius

I haven't had one iota of issues with my wiring harness. It was amazingly easy to install and I am grateful for it! Thanks you.

I love my trailer hitch! I have told many people about how easy it was to install and how etrailer is the best, giving excellent advise on how to install, customer service, and price. I am thinking of selling my car and getting one that can tow my little tear camper better and I thought of you if the vehicle I purchase doesnt already have a tow hitch.
Mari L - 04/30/2018

2012 Toyota Prius

Perfect fit. No worries lights work flawlessly! Only thing that could be better would be the old trailer light install before LEDs, only needed pigtail and ten cents worth of splicing connectors. Still with new LEDs and newer vehicle wiring your product is the best.

Show More Reviews

See what our Experts say about this Tekonsha Custom Fit Vehicle Wiring

  • Power Wire Connection Point Location for Tow Ready Trailer Wiring Harness on a 2011 Toyota Prius
    Apparently on a 2011 Toyota Prius, the battery is located in the rear cargo area. it is underneath the floor covering in the rear corner of the cargo area. Take a look at the installation details for the Tow Ready Wiring Harness, # 118505, which shows the battery location.
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  • Is There a Trailer Wiring Harness that Fits 2013 Toyota Prius
    We have custom fit trailer wiring harnesses that fit your 2013 Toyota Prius like the Tekonsha part # 118505 which I would recommend highly. It installs easily, is compatible with the LED taillights you have, and is our most reliable option so it's the way to go.
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  • Help with Installation of Tekonsha T-One # 118505 on a 2017 Toyota Prius
    It sounds like you are having trouble either with step 2 or step 6 in the installation instructions of the Tekonsha T-One # 118505 on your 2017 Toyota Prius. You will find the connector for step 2 inside the vehicle behind one of the side panels (picture C) while the connector for step 6 is located under the Prius on the driver's side (picture E). If you are unable to disconnect those connectors then I would either let a second pair of hands give it a try or take your vehicle to a shop....
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  • 4-Flat Wiring Harness for a 2013 Toyota Prius 4-Door Hatchback
    The best trailer harness for your 2013 Toyota Prius 4-Door Hatchback is going to be the Tekonsha T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector item # 118505 you were looking at. 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. This will provide you with a 4-flat connector to control your accessory lights. I have linked an installation video.
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  • Trailer Wiring Recommendation for a 2010 Toyota Prius
    Yes there are wiring harness for the 2010 Toyota Prius. I have included a link to the wiring main page for your vehicle. There are 2 options available. The most popular option is # 118505. I have included a link to the installation details and a link to a video that covers some of the features of the wiring harness for you.
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  • How To Install Tow Ready Custom Fit Vehicle Wiring # 118505 On 2009 Toyota Prius
    The item you selected, Tow Ready Custom Fit Vehicle Wiring, part # 118505, plugs in-line with the vehicles tail light connectors. You will need to access the wiring behind the tail light by removing the plastic trim pieces inside the vehicle. The connector with the Yellow wire will connect to the drivers side tail light harness. Then, you will need to connect the White wire which is the ground to a clean metal surface. You can use an existing bolt to connect the ground wire. Then, you...
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  • Adapter Recommendation for Towing a Trailer with a 7-way with a Tow Vehicle that has a 4-Way
    Sounds like your tow vehicle has a 4-way and you are looking or an adapter so that you can tow your trailer with surge brakes and a 7-way connector. For that you would want the part # 30717. The extra wires would just get taped up and out of the way. I attached a review video for you to check out as well.
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  • Can a 4-Way T-One From a 2005 Toyota Prius Fit On a 2015 Nissan Rogue?
    Your T-One Vehicle Wiring Harness # 118505 that you likely have on the 2005 Toyota Prius has a vehicle specific connector that you can connect directly to the tail light wiring so that you don't have to splice any wiring. The T-One Vehicle Wiring Harness # 118480 that fits your 2015 Nissan Rogue will have a different end connecter that connects to the tail light on the Rogue as it is vehicle specific. The wiring is likely also longer as the Rogue is a larger vehicle so it will need to...
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  • Solutions for Towing a Trailer with a 4-way with a Tow Vehicle with a 7-Way Connector
    I think I have a better solution for you. I would recommend you get an Adapter 7 Pole to 4 Pole # 47345. You would simply just plug this product into the 7-way on your new tow vehicle and you would have a functioning 4-way. This option is nice too because if at some point you do have a trailer with a 7-way connector on it you would still be able to tow it. If you do really want to cut off the 7-way and install a 4-way you could still do this. You would just need to wire by function. For...
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  • Trailer Wiring Harness Options for a 2010 and Newer Toyota Prius
    The third generation Toyota Prius starting in the 2010 model year can use Curt trailer wiring harness # C56147. You could also use # 118505 both it and the Curt harness plug in line with the vehicle tail lights to get the correct signals. I have included instruction links for both wiring harnesses and a video showing installation for harness # 118505.
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  • Can Trailer Wiring Harness From 2010 Toyota Prius Fit 2016 Toyota Prius
    The 2016 Prius you have uses a different wiring harness than the 2010 model, so therefore the wiring harness from your 2010 will unfortunately not work on the 2016. For your 2016, the # C56353 is available which is a confirmed fit. This harness includes a converter that is needed for the separate wiring on your Prius and also plugs in to a connector in your rear cargo area. You'll then need to run the hot lead wire to the battery of the Prius as shown in the FAQ article I've linked for you.
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  • Recommended Trailer Wiring for a 2007 Toyota Prius
    The Tekonsha T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118505 is the wiring that I recommend for you to use for your 2007 Toyota Prius. Although all of our manufacturers offer great wiring choices, Tekonsha sits above the rest because their equipment tends to last longer because of their design. Not that other wiring options are terrible, Tekonsha is focused more on electronics so they know their stuff. You can either keep the 4-Pole connector in your trunk, or...
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  • Which Trailer Wiring Harness for 2008 Toyota Prius
    If the trailer you'll be pulling has minimum lighting, one stop/turn/taillight on each side at the rear of the trailer, or if the lamps are LEDs then the Tow Ready # 118505 would work just fine for you. The Curt # C56147 has a slightly higher capacity, so if you have more lamps on your trailer other than the minimum amount mentioned above, the Curt harness might be a better choice. I've linked you to an install video for the Tow Ready harness. The procedure for the Curt harness would...
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  • Troubleshooting Hybrid Error Code After Trailer Wiring Install of 2010 Toyota Prius
    The video you referenced shows the Tekonsha kit part # 118505 install on a 2010 Toyota Prius like yours which is basically the exact same install as the Curt part # C56147 that you have. If there's a Hybrid Error warning light coming on I would suspect the issue is related to the battery wire of the kit. Make sure it's attached to the positive terminal of the battery securely and no exposed wire on this circuit is making contact to anything metal. It's also possible the battery terminal...
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  • Can a Brake Controller Be Installed in a 2006 Toyota Prius
    First thing you need to do is check the owners manual of your 2006 Toyota Prius to determine if there are any restrictions on towing with your vehicle. Priii weren't exactly designed for towing so you may have to rethink your towing vehicle. But maybe not, your owners manual will tell you for sure. With that in mind it is possible to install a brake controller in basically any vehicle. If you do not have trailer wiring you will need to start with a 4-way. For that you would want the #...
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    Image 1 for
  • Recommended Hitch and Towing Accessories for 2010 Toyota Prius
    I'd recommend the Draw-Tite Class I hitch, part # 24847. The hitch does not include a ball mount. And you will need the appropriate trailer ball, # 19256 for a 1-7/8 inch ball or # 19258 for a 2 inch ball. You'll also need a trailer wiring harness, # 118505. The hitch has a 2000 lb towing/200 lb tongue weight capacity, but that capacity might be limited by the capacity of the vehicle if it is lower. I examined an online copy of the owners manual, and was unable to find a towing capacity...
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  • Adapter to Convert 4-Pole on Tow Vehicle to 7-Way Trailer Connector on Trailer
    It sounds as if you are needing a 4-pole to 7-way adapter like part # 37185. The adapter would plug into your existing 4-pole, with 4 wires remaining. The white wire would ground to the vehicle, the blue wire would carry the output from a brake controller and the black wire would run to the vehicle battery to provide power for any trailer mounted accessories requiring 12-volt power. The purple wire is typically used to power trailer-mounted reverse lights. If your trailer does not have...
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  • Trailer Hitch Recommendation for a 2010 Toyota Prius
    We do have trailer hitches designed to fit the 2010 Toyota Prius and I have attached a link to our trailer hitch fit guide for you to check them out. Before installing a trailer hitch, I recommend checking your owners manual for manufacturer restrictions. We know that on some models of the Prius Toyota states a trailer hitch should not be installed for hitch mounted accessories or towing. You can also check with your local Toyota dealer. If you still want to install a trailer hitch or...
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  • Hitch Recommendation for a 2010 Toyota Prius
    We do have all the components needed for your 2010 Toyota Prius to tow a trailer, BUT that doesn't mean it would be recommended as it sounds like it would void your warranty. For a hitch you could use the Draw Tite Hitch part # 24847. See install video. For trailer wiring you would want part # 118505. For a ball mount part # 3593. 1-7/8 inch hitch ball part # 19256.
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  • Will Adding a Trailer Hitch Affect Gas Mileage on a 2010 Toyota Prius
    The plastic appearance panel on your 2010 Toyota Prius will stay in place with Draw-Tite trailer hitch # 24847 installed so you won't have to worry about that. The hitch will add some extra weight to the vehicle, less than 25 pounds, and minimal drag, if any. If you are in to hypermiling then you might be able to notice a slight decrease in mileage, if there is any at all. The way a person drives a vehicle has more affect on fuel economy than adding a hitch would. Please consult the...
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  • Can a Class I Hitch on 2012 Toyota Prius Carry a Jazzy Power Chair and Carrier
    All hitches offered for your 2012 Toyota Prius are light-duty Class I types like the Draw-Tite # 24847 that you referenced. You can see all available hitches using the link at right. All share the same 1-1/4-inch receiver size and 200-lb tongue weight rating. Pride Mobility makes many versions of the Jazzy power chair and the 1450-Series for example weighs in the range of 200-lbs without its 52-lb battery. Therefore that particular chair by itself - even before you add the weight of a...
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  • How to Transport a Wheelchair with a 2012 Toyota Prius
    The only way you are going to be able to transport your scooter with a vehicle that has a Class I hitch like your 2012 Toyota Prius would have would be a small trailer. If you do not have a hitch yet you would want the part # 24847. For trailer wiring you would need the part # 118505, for a ball mount # 3593, and then for a 2 inch ball # 19258.
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  • Parts Needed to Tow Small Rental Trailer Behind 2010 Toyota Prius
    To tow a trailer with your 2010 Toyota Prius you'd need a hitch like # 24847 that you referenced, wiring like the Tekonsha # 118505, and then a ball mount # 3593 with a hitch ball # 19256 and you'd be set.
    view full answer...
  • Trailer Wiring Harness for 2008 Toyota Prius that Can Be Used with LED Taillights
    We have trailer wiring harnesses that fit your 2008 Toyota Prius and are compatible with LED trailer lights like the # 118505. We don't have taillights for trailers that match exactly what you are looking for but we do have the part # STL178RB which is oval shaped and has a ring around the perimeter for it that offers the stop and turn signal function.
    view full answer...

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