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

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

Item # 118770

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Custom Fit Vehicle Wiring

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Powered Converter 118770
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  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • Tekonsha
  • 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. Call 800-298-8924 to order Tekonsha custom fit vehicle wiring part number 118770 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
  • Q & A (3)
  • Videos (1)
  • Photos
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Tekonsha Custom Fit Vehicle Wiring - 118770

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.


  • 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 rear cargo area
    • 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: 5 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 in your rear cargo area. You will have to remove the rear threshold and some interior lining to access this 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 connector will be stowed in 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.

118770 Tekonsha T-1 T-Connector - 4 Wire - Modu-Lite Converter

118770 Installation InstructionsInstallation Details 118770 Installation instructions

This Product Fits The Following Vehicles

2014 - 2018 Volvo S60

2014 - 2019 Volvo S60

2019 - 2019 Volvo S60 excluding R-Design

California residents: click here

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

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Tekonsha Custom Fit Vehicle Wiring - Trailer Hitch Wiring - 118770 Review

Speaker 1: Today we're taking a look at the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector. This product fits certain years of the Volvo S60. To ensure or double check that this is a fit for your vehicle, you can always use the Vehicle Fit Guide at etrailer.com. This unit, once installed, provides a 4-way flat connector at the back of your vehicle to power your trailer's signal lights. This connector is compatible with 5-pole, 6-pole, and 7-pole adapters. Adapters are sold separately.

And it comes with a dust cap for the 4-way flat connector. That way you can cover up the connection points whenever your plug's not being used. The cap is actually tethered to the plug housing so you don't have to worry about misplacing that or losing it.All the wires run to this black box. This is the included Module Lite. This ensures that your vehicle's wiring matches that of your trailers.

This powered module connects directly to the vehicle battery to avoid overloading the vehicle's electrical system, and it does that through the wiring. It connects quickly and easily. All you need to do is locate the connection points in the rear cargo area. One of the connectors goes to the passenger's side of the vehicle. The other one favors the driver's side.

These are custom fit so they're going to match up perfectly with the ports on the vehicle and they snap lock together for a nice tight secure fit.Once you have the T-connectors plugged in, you'll then need to make a ground connection. That's your white wire with a ring terminal attached to it. You want to get that grounded to a suitable grounding point with the included grounding screw. Then you'll need to mount the converter box. You want to mount this to a safe, out-of-the-way location, and you can do that with the included double-sided adhesive tape provided in the kit.

Next, you'll need to run the hot lead to the vehicle battery. That's the short black wire coming out of the box. This gets connected to one end of the bundle with one of the included butt connectors. The other end of the bundle runs to the vehicle battery, gets another butt connector attached to it, and connects to one half of the fuse holder. The other half of the fuse holder gets a ring terminal attached to it and gets connected to the positive post of the vehicle battery.It does come with your 15 amp fuse, goes directly into the fuse holder, and it's got the cap that goes over to keep it safe and protected. Once you have that done, you can secure any excess or slack in your wiring with the included cable ties. Then once your installation is complete, the 4-way connector will be stowed in the trunk of your vehicle. You can pull it out when you need to use it and then roll it up and tuck it away when you don't. It is recommend that you use a small amount of dielectric grease on all your electrical connections, like the plugs on the vehicle and the 4-pole connector itself. That grease is specifically designed to prevent corrosion to the connection points. It's sold separately and available at etrailer.com. When it comes to the maximum amperage for the stop and turn lights, we're looking at five amps per circuit and for the tail lights, 7.5 amps per circuit. That's going to do it for today's look at the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector.


Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring

Do you have a question about this Custom Fit Vehicle Wiring?

  • Finding the Stop Light Switch Wire on a 2014 Volvo S60
  • Typically the location of the stop light switch is up and behind the brake pedal but you would need to use a circuit tester like part # PTW2979 to verify which one it is. The wire you are looking for will show power only when the brake pedal is pressed. If you check out the installation video (23:40 mark) that I attached you can see this testing being done on a 2012 Volvo XC90. If you don't already have a brake controller then I recommend the Tekonsha Prodigy P3 # 90195. This is...
    view full answer...

  • Trailer Hitch Recommendation for 2018 Volvo S60
  • Yes, the Draw Tite hitch part # 75916 that you referenced is a confirmed fit for your 2018 Volvo S60 and is a 2 inch hitch. For trailer wiring you'd then want the # 118770 which is a custom fit. If you wanted to do some towing you might be interested in etrailer ball mount kit # 989900. It comes with 2 ball mounts; one with a 3/4 inch rise or 2 inch drop and one with a 2-3/4 inch rise or 4 inch drop. It also includes a 1-7/8 inch ball, 2 inch ball, hitch pin with clip, and a storage...
    view full answer...

  • Parts Needed to Install Prodigy RF 90250 Trailer Brake Controller in 2014 Volvo S60
  • All brake controllers will require a hard-wired 7-way installation in your 2014 Volvo S60 since the car does not have a quick-connect brake controller port under the dash like many tow vehicles do. The linked page displays all wired controllers. You will need to use our brake controller installation kit # ETBC7 along with a 4-pole harness # 118770 in order to have the fully-functional 7-way on the car that is required to use the Prodigy RF brake controller # 90250. Once the 7-way...
    view full answer...

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Info for this part was:

Edited by:
Lindsey S
Installed by:
Cole B
Written by:
Alexander C
Updated by:
Isabelle B

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