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  1. Custom Fit Vehicle Wiring
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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 # 118489
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Custom Fit Vehicle Wiring

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Custom Fit 118489
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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. Includes tail light converter. 1-833-496-1390 to order Tekonsha custom fit vehicle wiring part number 118489 or order online at 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.
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  • Reviews (29)
  • Q & A (0)
  • Photos
  • Why etrailer?

Tekonsha Custom Fit Vehicle Wiring - 118489

  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • 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. Includes tail light converter.


  • 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
  • Includes a tail light converter to ensure that your vehicle's wiring matches that of your trailer
  • 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: 7.5 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 installation is complete, the 4-way flat connector will be stowed 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.

Tail Light Converter

A tail light converter 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. The tail light converter combines 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.

118489 Tow Ready T-1 T-Connector - 4 Wire

Installation Details 118489 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 - 118489

Average Customer Rating:  5.0 out of 5 stars   (29 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. Includes tail light converter.


Easiest connections ever. Requires no cutting, taping etc. FYI, if your break lights don't work, then you need to switch over the trailer lights to LEDs.


I bought a hitch and wiring for my car. Etrailer was awesome. They upgraded my shipping at no extra charge and then followed up to make sure all was well with my order. I thought a piece was missing from my order when it arrived. Without hesitation the service rep was very apologetic and willing to expedite the piece. It turned out it was in the box afterall. I put the hitch on and wiring connector on in a matter of a hour. It was so easy. I would definitely recommend etrailer and their products. Top notch and I appreciate it.


I watched the video before installing and everything plugged right in. Super easy...the trunk latch cover just pops up, there are two plastic trim clips that hold it down. Gently pry up with a trim tool or large flat screw driver. The yellow and red wires connect to the driver side and the green wire connect to the passenger side. The plugs are sized specific to the connectors and so worries about plugging into the wrong socket. Again, watching the video made install super easy. Fits directly to my 2007 Acura TL Type-S

2008 Acura tl

I have to say, this was a synch to install. I'm a 38 y.o. Female and one of the reasons why I bought this was it had a video that explained step by step. I didn't even read the paper instructions. I just followed the video and did install this all by myself in less than an hour. In fact the longest part was the hour I had to wait for the drill battery to charge since it was dead when I went to drill the ground wire! Piece of cake on my acura tl 2008.


After 1 year the all of the wiring is still working great! It was very easy to install with the right connectors for my 06 acura tl. Highly reccomend this product

One year later and the plug is still in good shape!
James S - 09/10/2020


The wire harness is perfect. Plug and play. No splicing, no figuring out where the voltage is at, and no screwing up your OEM set-up. Highly recommend if your getting the tow hitch.

2006 Acura TL

Truly a plug-and-play harness. Instructions were brief, but sufficient, since there is clear color coding of the wires and there is no way to plug it incorrectly. Tested - works as it should. Good product.

2006 Acura TL

This is a plug and play install. No cutting or splicing wires. I installed it in 5 minutes and all the lights on my trailer work perfectly. I watched a video of the install on youtube and did the same. Great product with easy install.

2006 Acura TL

Easy install-took less than 10 minutes. Great website and videos-The most thorough I have seen. Super fast shipping.

2005 Acura TL

Use this product on a 2005 Acura TL, only took 5 days to receive
Watched instalation video on etrailer website and I was able to do it in 15 minutes

2008 Acura TL

Installation was a piece of cake and this kit works flawlessly. Great price too! I would definitely buy again if needed.


Great ProductThis harness was super easy to install - 20 minutes and it was done with no splicing.

2005 Acura TL

The wiring kit is very easy to install on an Acura TL. Takes about 20 minutes if you read the instructions and do it right. Just take your time. If you rush it, you will mess it up.

Acura TL

Product works fine with my Acura Tl and YouTube installation video really helps.

2006 Acura TL

plug and play - very easy to install in my Acura TL.


Loved the plug and play part of this setup. Entire install was easy and fast.

2005 Acura TL

Seems to be great quality and set up was an absolute breeze. Shipping was super quick as well.

2004 Acura TL

Trailer hitch was delivered in less time than expected and it was exactly the right birthday present for my boyfriend! Should have been exactly right, he picked it out. :-)


Very simple to install couldn’t be any easier. Works great over a year later.



Still works great after a year

2005 Acura TL

Online video made install a breeze. Very happy.

2005 Acura TL

pnp perfect

2006 Acura TL


Show More Reviews

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

  • Trailer Turn Signals Flash Very Dim and Show Inconsistent Voltage
    First, I would not immediately dismiss a bad ground simply because there are so many of them in an electrical system that could be faulty. While there may be some fluctuation in the voltage when the turn signal is cycling on and off, it seems like the problem you are having is different than that. There is an easy way to determine where the problem is. With a trailer disconnected, check the voltage on the turn signals at the vehicle side trailer connector. If they are weak there you know...
    view full answer...
  • Wiring Harness On 2008 Honda Odyssey Shows Voltage When Car Is Turned Off
    When you install the Curt Custom Fit Vehicle Wiring, part # C56161 on your 2008 Honda Odyssey, you will show voltage at the 4-way connector pins. You will not have an amperage draw until you hook the connector to your trailer harness and a load is placed on the system. If you wish to leave your trailer plugged in when parked, one way to stop current draw would be to remove the in-line fuse. You will need to remember to put the fuse back in when ready to tow and that can be a hassle at times.
    view full answer...
  • Trailer Clearance/Marker Lights Do Not Light Up But All Other Lights Work
    It sounds like there is some issue in the wiring or possibly a new ground location is needed for the affected lights. Inspect the wiring from the front to the back and look for any pinched or frayed wires and repair as needed. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces. The light grounds should also be attached to clean and corrosion...
    view full answer...
  • Low Voltage on Curt Wiring Harness When Lights On
    What you are describing seems to be common in some Curt trailer wiring harnesses that use a powered converter. If you were to pull the fuse out of the fuse holder it should not show power any more (with the vehicle on or off). It sounds like you have a weak ground, loose butt connector or perhaps a crimp in a wire. Check all your ground wires to verify they are securely attached to a clean, bare metal surface. These checks should include the ground connector on the tow vehicle, the ground...
    view full answer...
  • Troubleshooting Dim Trailer Lighting
    Most likely it's a ground issue. When we see trailer lights not being fully bright the issue is almost always an insufficient ground. I would recommend running a jumper ground wire from the light assemblies to the main ground of the trailer and you should see the lights start working like normal. I attached a help article on troubleshooting trailer wiring for you to check out as well.
    view full answer...
  • Troubleshooting No Brake Lights on 2004 Acura TL with Trailer Connector Installed
    Lets see if we can get you going. Let me know if any of the suggestions that I make sound like they will work or if you have already checked the suggestions I make here. When you checked the output at the 4-Way connector was the trailer hooked up? If so unhook the trailer and recheck the voltage. If you have twelve volts at the green and yellow connections on the 4-Way harness without the trailer connected then the problem is most likely a ground issue on the trailer side. Check all of...
    view full answer...
  • What Should the Voltage Output Be at the 4-Way Plug on Curt T-Connector Wiring Harness # 56016
    When you test the 4-Way on the Curt T-Connector Wiring Harness, part # 56016, at the rear of your vehicle, it should show now power on all 3 pins with the lights off. If you have the vehicle head lights on, you should have around 12 volts at the brown (tail lights) pin only. If you apply the brakes, you will have about 12 volts at the green (right turn and brake) and yellow (left turn and brake) pin with the head lights off. If you turn on the right turn signal, you will have around 12...
    view full answer...
  • Where Does a Trailer Wiring Harness Install on a 2006 Acura TL
    The trailer wiring harnesses for the 2006 Acura TL, such as # 118489, plug in line with the tail lights on the vehicle. I have linked the instructions for this harness and a video showing an example installation for you.
    view full answer...
  • Trailer Right Brake Light On All the Time, 12 Volts on All Pins on Trailer Towed by 2008 Dodge Nitro
    It sounds like there was a short or there is still a short that is causing some problems. To determine if the problem is on the vehicle side or the trailer side there is a test you can do. First unplug the trailer from your 2008 Dodge Nitro. Then use a circuit tester such as # 40376 to test the wires going into the converter box and the wires coming out. Someone will need to sit in the vehicle and activate the lighting functions while you test. If all of the wires are correct coming from...
    view full answer...
  • LED Trailer Lights Illuminate Even When No Lighting Function Is Activated on the Tow Vehicle
    It is not uncommon for some trailer wiring harnesses like the Curt # C56161 to pass a small amount of power even when no vehicle light function is activated. If used along with super-efficient LED-type trailer lights this can result in low-level illumination when you least expect it. This low power will not light up standard incandescent bulbs but it will sometimes be enough for LED lights that typically use only about 1/10th the power required by incandescent lights. The two solutions...
    view full answer...
  • Curt Wiring Harness Short to Ground Turns Off Cruise Control on a 2005 Acura TL
    It sounds like there is a short or possibly a broken or bent pin in the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Item # C56231 for your 2005 Acura TL. Check where it connects to the vehicle tail light wiring and see if the pins in the connectors for the wiring harness and vehicle are intact and there is no corrosion. The wiring harness does not have to be grounded to the battery or powered by the battery. If you are getting voltage on the white ground...
    view full answer...
  • Will Draw-Tite Trailer Hitch 24755 Fit a 2007 Acura TL Type S
    The Draw-Tite trailer hitch # 24755 is designed to fit all models, including the Type S, of the 2007 Acura TL. I have included a link to the installation instructions and a link to a video showing a typical installation for you. This hitch comes with a ball mount, pin, and clip. For a 1-7/8 inch ball use # 19256 and for a 2 inch ball use # 19258. For trailer wiring use # 118489. I have included links to the instructions and a video for the wiring as well.
    view full answer...
  • Picture Request for a 2006 Acura TL with a Hitch Installed
    I attached a couple pictures of an Acura TL that is the same generation as your 2006 Acura TL. I also attached installation instructions for this hitch for you to check out. If you plan on doing some light towing you may be interested in purchasing the following products to complete your towing setup: Tow Ready Custom Fit Vehicle Wiring # 118489 (Instructions attached) Hitch Ball with 1-7/8 inch Diameter and Medium Shank # A-80
    view full answer...
    Image 1 for Image 2 for
  • Troubleshooting Voltage Drop When Connecting LED Trailer Lights to Wiring Harness
    It sounds like the ground connection often in the mounting hardware of your lights is not connected well. This ground needs to be bare metal to metal and free of all corrosion and debris. If with a clean ground you still are not getting the desired function, you will need to add more resistance to the light fixture by adding a load resistor like the LED Light Bulb Load-Resistor Kit # DI34ZR to draw the desired power for proper function.
    view full answer...
    Image 1 for
  • Troubleshooting Voltage at 4 Pin Flat Trailer Connector
    You should be getting 12 volts from each function when that function is active. The amperage will be less and can vary between functions. You can use a multimeter like # PT89ZR to check this. If you have a specific part number you want me to check into for the amperages let me know as these are year/make/model specific and can even vary slightly between brands.
    view full answer...
  • Is Drilling Required To Install Curt Trailer Hitch # 11321 On My 2005 Acura TL
    Installation of the Curt Trailer Hitch, part # 11321, does require drilling on your 2005 Acura TL. The hitch will attach to the bumper beam, so it does not require trunk access. The Curt Trailer Hitch # 11321, includes a drawbar, pin and clip. To complete your towing setup you may be interested in the following items: 1-7/8 Inch Hitch Ball, part # 19256 2 Inch Hitch Ball, part # 19258 Vehicle Wiring, part # 118489 If you plan on using a hitch mounted bike rack, you will need to use a...
    view full answer...
  • Can 2008 Acura TL Tow 1,000 lb Jet Ski Neighborhood
    I looked up the towing capacity of your 2008 Acura TL and found it can tow up to 1,000 lbs so with a hitch installed like the Curt # 11321 you'd be able to tow your jet ski trailer as long as it's under the 1,000 lb capacity of the vehicle. For trailer wiring you'd then want the part # 118489 which is a custom fit and reliable. For a ball mount you'd then want # 3594 and hitch balls # 19258 for a 2 inch ball or part # 19256 for a 1-7/8 inch ball.
    view full answer...
  • Difference in Hidden Hitch # 60814 and Draw-Tite Hitch # 24755 For 2008 Acura TL
    You are correct the Hidden Hitch Class I 1-1/4 Inch Hitch, part # 60814 (no longer available), and the Draw-Tite Class I 1-1/4 Inch Hitch, part # 24755, are the same hitch produced by Cequent Performance Products. Both of the hitches will fit your 2008 Acura TL. The # 24755 Draw-Tite hitch does not include the ball mount and pin and clip. This hitch is sold to someone that might be using the hitch to carry a bike rack on the rear of their vehicle and will not need the ball mount. I am...
    view full answer...
  • Troubleshooting Wrong Bulb Filament Lighting Up with Running Lights
    It could be that there is either a mis-wired trailer connector, a mis-wired light or that the presence of corrosion in a connector has the running light circuit linked to the turn signal circuit. You could also have a bad bulb with a damaged filament. You can try a new bulb to rule that out as a cause. Check all your wiring connectors for any signs of trapped dirt, moisture, corrosion or discoloration and clean or replace as needed. You can also check that your stop/turn/tail light, such...
    view full answer...
  • Recommended Hitch and Accessories for Towing 4X8 Rental Trailer w/ 2006 Acura TL
    Although they have the same weight capacity, I'd rather see you use the Curt Class I hitch, part # 11321. Rather than bolting to the underside of the trunk pan like the Draw-Tite, the Curt hitch bolts to the underside of the rear bumper beam which in my opinion would make for a sturdier installation. The hitch has a 2000 lb towing/ 200 lb tongue weight capacity that you'll want to remain well below. You'll also need the following to complete your towing set-up: Trailer wiring harness,...
    view full answer...
  • How to Find Rise/Drop of Ball Mount Needed for Towing Small Aluminum Boat with 2007 Acura TL
    When we installed the Draw-Tite # 24755 Class I hitch on a 2007 Acura TL, we found that the inside top edge of the receiver tube sat 10-1/2 inches above the pavement. To determine which ball mount would place your trailer as close to level as possible, you'll need to put the boat trailer up on it's jack so it's level, then measure from the bottom edge of the coupler to the ground. The height difference between 10-1/2 inches and the level trailer coupler height equals the amount of rise/drop...
    view full answer...

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