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  1. Tow Bar Wiring
  2. Tow Ready
  3. Diode Kit
  4. Splices into Vehicle Wiring
  5. Universal
  6. Tail Light Mount
Tow Ready Tail Light Isolating Diode System with 4-Pole Connector

Tow Ready Tail Light Isolating Diode System with 4-Pole Connector

Item # TR118821
Our Price: $65.50
You Save: 45%
Tow Bar Wiring

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This combined diode system features a Y-harness that allows your RV to power the lights on your towed vehicle without the vehicle sending electrical feedback to the RV. The 2-diode system does the work of 4 and protects both electrical systems. Great Prices for the best tow bar wiring from Tow Ready. Tow Ready Tail Light Isolating Diode System with 4-Pole Connector part number TR118821 can be ordered online at or call 1-636-306-4830 for expert service.
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Tow Ready Tow Bar Wiring - TR118821

  • Diode Kit
  • Splices into Vehicle Wiring
  • Universal
  • Tail Light Mount
  • Tow Ready

This combined diode system features a Y-harness that allows your RV to power the lights on your towed vehicle without the vehicle sending electrical feedback to the RV. The 2-diode system does the work of 4 and protects both electrical systems.


  • Kit includes everything required to wire vehicles with a 2-wire system for towing behind a motor home
    • Y-Harness with 1 driver's-side and 1 passenger's-side diode
      • Each diode contains a tail light and combined turn and stop feed
    • 4-Pole flat connector extension
      • Runs along your tow bar
      • Connects RV wiring system to the Y-harness
    • 8 Wire connectors, 1 ring terminal and 4 zip-ties
  • System connects your RV turn signals, running lights and brake lights to your towed vehicle's lights
  • Mounting bracket for 4-way flat connector (18144) sold separately
  • 1-Year limited warranty

Tow Ready Tail Light Isolating Diode 2 wire to 2 wire diagram

Tow Ready Tail Light Isolating Diode 2 wire to 3 wire diagram

Please note for 3-wire system on towed vehicle: With this kit, the towed vehicle's brake lights will function as both the brake and turn lights. A wiring converter (118158; sold separately) and 2 additional diodes (also sold separately) will be needed if you want to retain separate turn and brake signals.

118821 Tow Ready Tail Light Isolating Diode System with 4-Pole Connector

Installation Details TR118821 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Satisfaction Score:

Customer Reviews

Tow Ready Tail Light Isolating Diode System with 4-Pole Connector - TR118821

Average Customer Rating:  4.8 out of 5 stars   (196 Customer Reviews)

This combined diode system features a Y-harness that allows your RV to power the lights on your towed vehicle without the vehicle sending electrical feedback to the RV. The 2-diode system does the work of 4 and protects both electrical systems.


Instructions were helpful, I ran the wire through the inside of my Mini Cooper. Real easy, did not needed to lift the car. Works well


As it took >8mos to get the tow hitch for to use this wiring with, I have only used it once. however, I will say that install was very easy with the video on your website and it did work flawlessly.


I have yet to install the wiring harness but will do so in the next few weeks in preparation for a trip this summer. Inquire again next year and I will respond.

I installed and used the wiring harness last year from Florida to Massachusetts and back. It was easy to install and worked perfectly the whole trip.
Norman - 03/14/2022


I have been using trailer for years. Never had a single issue with product or delivery!


Works perfectly had no problems with installation doing it my self

2019 Jeep Cherokee

Worked as advertised, good product with easy installation

Works great!
Denny - 07/20/2022


I’m giving it 5 stars only for the fact that it works as described but instructions lack on its installation I had to go online and lookup the manufacturer on how to hook it up on tail lights..

Sorry for the installation trouble. Here is an installation video for a 2019 Jeep Cherokee:
-- Etrailer Expert Sierra K - 12/22/2021

1997 Suzuki Sidekick

The tow ready tail light isolating diode system is what i need but the installation instructions does not apply to my vehicle. I have a 1997 Suzuki sidekick JX. The instructions says, remove the cover to compartment where jack is stored, to access the wiring harness and find plug. My jack is stored under the passenger front seat. No storage compartment in rear of vehicle. So far i haven't found the harness I'm suppose to unplug more later when and if i find it.


Needed help from etrailer's tech support, as color code was different.
Tech support was great. Item works as intended!

Have towed thousands of miles with no problems!
Chuck - 01/27/2022


Been using this product now for well over a year. Works flawlessly.


Was able to travel a lot of states with the hook up, all worked as expected and I appreciate all the help Roger gave me. Will definitely purchase from etrailer in the future.


The quality is top notch. Fits my car like Cinderella's slipper.


This has worked perfectly. It was easy to install and is still working great after a year of use.

Wonderful! Still working perfectly.
Brittainy - 06/02/2022


The system was easy to understand and install. Works as expected.

2019 Ram 1500

Have not installed the wire
ing kit as
of yet

2019 Dodge Ram Pickup

I am very pleased with the Demco setup. I'm towing my 2019 Ram 1500 behind 2017 Tiffin Phaeton bus. With the help of etrailer videos I was able to install the base plates, light wiring, brake system and battery charger completely by myself. It took some effort and a couple of days but save lots of money and know that it is done right.


easy to install I am very happy with your product, the video you provided was a great help, I just moved the brake indicator LED to the Motorhome dash instead of the tow vehicle and I provided power to the controller from the motorhome.


very good parts.


Fit perfectly. I like the new coating. Doesn’t flake off like the old one did.


easy install worked perfectly.


I replaced a previous version and found this one was easier to installed.


Installing this kit was no small feat. It required disassembly of the rear bumper and taillight assemblies, as well as snaking the wiring - intelligently - all the way from the back to the front. However, once installed it's been performing admirably for over a year and 10k miles of towing.


Knowledgeable staff on what will work and what you should avoid . The Videos are super helpful and very informative and they tell you what would be the better product not just sell you the most expensive products.

This wiring was easy to make all the connections. The hardest part was getting the wiring from the back lights through the frame and body up to the front connection. Once that was completed the remainder went pretty quickly.
Dave E - 05/12/2021


Easy install and works flawless. Our second time using this product with great results.

Still working with no issues
Jack - 12/28/2021


I used this product with Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
Item # C56407 in order to prevent splicing into the vehicle wiring harness. It was more expensive but it created a plug and play solution for my gladiator Jeep. Follow the videos to a t and you cannot go wrong also follow the attached diagram if you are going use my trick or wire by splice. It will save you some trouble shooting time.

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