The best technical support and full Custom Fit Vehicle Wiring installation instructions. Lowest price Tundra Custom Fit Vehicle Wiring guarantee and expert service. Toyota Tundra, 2002 Custom Fit Vehicle Wiring by Tow Ready are available from For expert service call 800-298-8924 to order your T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector part number 118378, or order online at
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Tow Ready Custom Fit Vehicle Wiring for the 2002 Tundra by Toyota

Tow Ready Custom Fit Vehicle Wiring

(43 reviews)

Code:   118378



Shipping Special

Shipping Weight: 1.2 pounds


T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 2002 Tundra by Toyota

Quickly and easily install a 4-way trailer connector on your Toyota Tundra 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 Toyota Tundra 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 point along frame rail
    • Plug in connector
    • Plug in fuse holder under hood
  • Includes ModuLite to ensure that your Toyota Tundra'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: 7.5 amps per circuit
  • 1-Year limited warranty


This custom-fit T-One connector plugs into your Toyota Tundra's wiring harness, which is located at the rear, along the driver's-side frame rail. Once you've plugged in the tow harness connector, locate the gray connector between the truck's battery and the fender at the front of your vehicle. Plug in the fuse holder wiring harness. Then attach the ring terminal at the opposite end of the harness to the positive terminal on your truck's battery. Insert the included 10-amp fuse into the in-line fuse holder.

Once installation is complete, the 4-way flat connector will be stowed beneath your Toyota Tundra, near the trailer hitch. A mounting bracket (sold separately) is recommended to keep the connector secure.

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 Toyota Tundra'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 Toyota Tundra operate.

With a ModuLite, your trailer's lights will be powered without overloading your Toyota Tundra'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.

118378 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

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 Trailer Wiring Harness Installation - 2002 Toyota Tundra

All right today on this 2002 Toyota Tundra were going to install part number 118378 from Tow Ready. All right, the first thing we need to do is go ahead and install a fuse holder by the battery. All right, now therell be a gray connector between the battery and the fender. Well take the cap off, well install our wire harness. Now, in some vehicles you can see these connectors and some dont, so it may be a good idea to go ahead and move the battery out of the way to find it. And also, some vehicles have a connector already installed to the hot lead to the battery.

However, a wiring harness uses a higher amperage, you would have to remove it and install the new one. In this case its nonexistent so well go ahead and start fresh. Well remove the cap and then go ahead and connect it to a positive side of a battery. All right, well take a moment to use a couple of zip ties to secure the wire harness and then well go ahead and add our 10M fuse. Well put the cover on top of it and well move to the back of the vehicle.

Well locate the plug and install it there. Our connection point will be located behind the bumper just past the drivers side frame rail underneath the bed of the pick-up located right here. Well take the cap off and well install our wire harness. Well move away from it towards the center of the vehicle. Okay, well connect some of the sheet metal and attach our module with adhesive to a sheet metal.

Then well route our wire to the center of a vehicle to the license plate holder. And well take some zip ties to secure our wires. And with that that will finish it for our install of part number 118378 on our 2002 Toyota Tundra.

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Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118378

Average Customer Rating:  4.9 out of 5 stars   (43 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.

- 118378

by: Dan C06/20/2012

Needed this harness for my 2002 Tundra. The Tundra owners manual leads you to believe that the factory harness is ready to haul a trailer, but this is not accurate. I installed the T-One Vehicle Wiring Harness with 4 Pole Trailer Connector with no difficulty in about an hour (and that was taking my time!). Instructions were clear and had good photos. Product arrived faster than I expected, and customer support was quick to answer a question about which rear truck connector to use (it is NOT the connector just behind the license plate, but in my case over on the far left side behind the tail light). I will definitely shop at Etrailer again. 45011

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by: Bob T08/29/2013

I've had a Hidden Hitch and wiring harness on my Toyota Tundra for a number of years. When I needed to get a 7 way plug I found that the old wiring didn't work. So I repmaced it and added a plug. The installation was easy and it works great. I wish there had been a single harness but replacing the old one and adding the 7 pin was very simple. I got great service from E-trailer and the video's were a good help. I'll use them again! 97496

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by: Giris08/28/2012

The harnesses plugged right up and worked perfectly. Great product! Communication from eTrailer was the best. Package tracking was weak and did not provide enough info. The eTraller website is easy to use & provides great info & instructions on the produce installation. Because the instructions were so good the purchase decision was no-brainer. I definitely make eTrailer my first look for this kind of product. 53315

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by: Mike04/23/2012

What can I say? This was the easiest install I've ever done. It literally took me 25 minutes to remove the old harness, then install and test this wiring harness and this is the first time I've installed anything like this. Etrailer responded to my online order within minutes and I had the kit delivered in 2 days. Great service, great product.......I'll be back in the future! Thank you etrailer. 38065

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by: Mike K06/30/2015

The harness I ordered was installed on mu 2001 Tundra in ten minutes. Easy, excellent delivery time and completely satisfied. The boat goes to the lake tomorrow with every light on the trailer working. The videos were an excellent source for me. Reading instructions is not my strong suit. 208423

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by: Matt in Upper Michigan09/18/2012

Had a positive experience with the wiring package I ordered through E-Trailer. Sales rep was knowledgable, friendly, and competent. Price and shipping costs were very fair.I received the package quicker than I expected and was happy to see the item was correct and exactely what i needed. 55094

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by: Ridge W.11/22/2013

The T one wiring harness for my 01 tundra worked perfectly , I watched the installation video on the website and when it arrived it took less than ten minutes to install . E - trailer's description and customer service were excellent I highly recommend them and their products. 108228

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by: Tom H10/08/2012

Received the product Friday afternoon and had it installed Saturday morning. Start to finish it took 20 minutes.I watched the on line vidio. Then followed the instuctions that were strait forward and clear. Very happy with the product! 56708

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by: Roy C10/01/2012

++This is my second order from etrailer. Both products have been constructed with heavier wiring than is available from other sources. Shipping has been prompt & safe and installation has been relatively painless.++ 56201

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by: Charles K. Childers06/20/2011

The T-0ne wiring harness was exactly as you described - a simple and easy plug-in installation. I am completely satisfied with my purchase as well as your highly efficient customer service. 17383

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by: MikeM04/25/2013

The product was just as ordered and delivered very fast. Setup was very simple (took 20 Min less if battery didn’t have to be moved) with normal hand tools. Would highly recommend 77785

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by: joe j05/18/2013

The product was great with easy and understandable directions and helpful pictures. they let you know continually about your order progress. Yes I would use this company again. 80807

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by: JAZ_Picayune10/28/2014

Very easy to install, perfect fit with the truck's existing connectors, good quality, and most important, worked flawlessly. I do recommend this product from 158279

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by: Danny Z08/02/2012

This product saved me somuch time and effort. Everything went together as it should. Excellent product and service. Never have I felt like such a valued customer. 50300

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by: Mike D. Ohio10/19/2012

Very impressed with the product. Works as advertised; it took me about 15 minutes to install it. Works like a champ Thanks saved me a lot of money 57639

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by: Keihan05/04/2015

The converter and the harness arrived in an easy-to-open packaging and with ample instructions. The device installed easily and worked as it was supposed to. 189717

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by: Tom Snowman07/11/2013

I am extremely satisfied with the product and especially the seevice. I placed my order on a Saturday and it arrived Thursday; works great! Thanks again! 89027

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by: Gregg K.05/09/2013

Had no issues installing this harness. May want to have a few extra zip ties available to satisfy individual tastes in the final dressing of the cables 79633

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by: Ben W.12/13/2012

Got my order in a timely fashion. Quality product and easy to install! I appreciate the instructional video on your website for installation. Thanks! 61278

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by: Donnie11/10/2012

The product plunged into my original wiring harness and function as designed. The price was competitive and the service was excellent. 59170

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by: harvey smith08/14/2014

I received the 118378 quicker than i thought. the product was very easy to install. i would reccomend the product to anyone. 146721

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by: mmdaddh08/11/2014

This harness was truly plug and go. Took me all of 20 minutes to install. Excellent design allowed for a very clean install. 146116

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by: STEVE T10/22/2014

Excellent service, product and delivery time! Saved money , time and hassle, will use again in the future! 157451

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by: Steve B02/01/2014

The wiring harness was delivered promptly, fit the older truck perfectly, and worked perfectly. Very satisfied. 115380

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by: Bob F03/21/2015

Shipping was much faster than expected. The part was exactly what I needed and works perfectly. 180093

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by: Ted Y.12/21/2013

Great product, great service, great price. very helpful and easy installation thanks to video:) 110823

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by: jim08/06/2014

Received my order very quick. Plugged it I'm, ready to go. Thanks for the quick response. 144718

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by: m.k.o.01/13/2013

I received the wiring harness right away but haven't installed yet I hope soon but thanks 62856

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by: christine06/05/2012

This was so easy to install. And it works perfectly. Would recommend this to everyone. 42856

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by: Steve W06/27/2012

I am very happy with the light assembly. Delivery was on time and everything works great! 45801

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by: Jerry M.08/29/2011

Have yet to install converter box on truck, but appears to be correct on for vehicle. 23005

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by: Chuck S05/11/2011

This wire harness was easy to install and fits perfectly. It works great 13600

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by: chad f10/14/2013

shipped very quickly, staff was great, parts worked as supposed too !;) 103797

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by: Andy B02/14/2011

Plugged right into factory harness. Instructions were good with pictures 7158

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by: jc12/05/2012

East to install. Just what the Dr. orde red 60753

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by: r novak11/12/2014

item installed and performed excellent 160570

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by: Jay J.08/01/2012

Easy to install, and worked first try. 50201

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by: Dave A02/27/2012

Fit perfectly.Installed in minutes. 32671

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by: Ed M.05/31/2012

Easy to install and it works.... 42128

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by: Gary N06/25/2015

Good quality part, easy install 206996

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by: Roy F08/25/2011

Great item VERY fast service 22804

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by: Ivan O. Cruz03/21/2012

Great Buying !!!Nice 34591

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by: Richard P.04/03/2011

A snap to install !! 10983


Ask the Experts about this Tow Ready Custom Fit Vehicle Wiring
Do you have a question about this Custom Fit Vehicle Wiring?

  • Availability of Brake Controller Harness for 2001 Toyota Tundra
  • If you are looking for a brake controller harness, there are none available for the 2001 Toyota Tundra. The 2001 Tundra did not have factory tow packages as an option, so a brake controller will have to be hard wired into the vehicle. You will need part # ETBC7 to create a 7 way plug at the rear of the truck. I will include a video on this kit. You will also need to install a 4 way connector. Toyota put the provision in for this so you will need part # 118378. Once you have these...
    view full answer...

  • Fuse Location for 118378 Tow Ready T-One Vehicle Wiring Harness
  • The 10 amp fuse for the # 118378 wiring harness is installed in the small yellow fuse holder, located on the smaller portion of the wiring harness that does not have the black converter box. This part of the harness would be connected underneath the hood of your 2002 Toyota Tundra. You would disconnect your negative battery cable, remove the battery hold down bracket, and slide the battery forward to locate the mating connector on your vehicle between the battery and fender. Remove...
    view full answer...

  • What Parts are Need to Add a 7-Way Trailer Connector to a 2001 Toyota Tundra
  • I do have a solution for you. In order to add a 7-Way wiring harness to your 2001 Toyota Tundra, you will need to start by adding a 4-Way, # 118378, if you need one. I have included a link to the installation instructions for this harness for you to view. With a 4-Way installed (or using an existing 4-Way if applicable) you will then need to install a 4 and 7 Way Installation Kit, # ETBC7. This kit includes everything you will need to install a functioning 7-Way on your truck. I have...
    view full answer...

  • Truck/Trailer Brake Lights Come on with Trailer Connected and not Using Brakes, 2001 Toyota Tundra
  • From what I have been able to gather, the 2001 Toyota Tundra did not come with a tow package that included trailer wiring connections. This could mean that it was done aftermarket and could have been wired incorrectly by a previous owner. Or there could be a bad ground issue causing the malfunction. I recommend checking the ground connections on the truck and trailer side connectors. They will need to be clean and free of corrosion. I spoke with one of our installers about this problem....
    view full answer...

  • Trailer Wiring Harness and Mounting Bracket for a 2002 Toyota Tundra
  • With the little bracket that is on the Hidden Hitch Trailer Hitch, # 87588, you should be able to directly attach Mounting Bracket # PK12711U. But you may not need it. The correct 4-pole for your 2002 Toyota Tundra is Tow Ready Custom Fit Vehicle Wiring, # 118378. To add a 7-Way I recommend using the 4 and 7 Way Installation Kit, # ETBC7. This comes with everything, including a mounting bracket, to add a 7-Way to the vehicle after you have installed a 4-Way. I have included a link...
    view full answer...

  • Trailer Light Not Working and Wiring Harness Show No Power on 2002 Toyota Tundra
  • First, what I recommend is checking the converter box in the trailer wiring, # 118378, to determine if it is the harness or the truck that is the problem. Use a circuit tester like # 3808 if needed to test the wires going into the converter box from the truck. If the signals are correct going into the box, you know that the truck is not the problem. Then test the wires coming out of the converter. If the signals are all correct coming out of the converter, the problem is somewhere on...
    view full answer...

  • Backup Light Connection For Activation of Surge Coupler Backup Solenoid on a Toyota Tundra
  • There are two options for energizing the backup solenoid on your trailer to allow you to backup. The first is an adapter like you mentioned. The 4 Pole to 5 Pole Trailer Wiring Adapter, # 20036, is designed to be easily installed and removed once the blue wire is spliced into the vehicles reverse light circuit, behind one of the rear tail lights. A circuit tester, # 3808 if needed, is required to determine the correct wire to splice the blue wire to. The second option is to use a 5-Way...
    view full answer...

  • Trailer Wiring Harness for a 2002 Toyota Tundra
  • I went out to the warehouse and pulled the trailer wiring harness, # 118378 to take a look at the plugs. There are actually 2 plugs, one that connects to a power receptacle on the truck for power and another one that plugs into the back where your receptacle is located. The harness does have 3 rows of plugs but the center row does have one pin right in the middle of the plug. This harness is the correct one listed for a 2002 Toyota Tundra. Take a look at the instructions for the harness...
    view full answer...

  • 7-Way Trailer Wiring and Brake Controller Recommendations for a 2002 Toyota Tundra
  • To install a 7-Way blade style trailer connector on your 2002 Toyota Tundra, there are a couple of parts you will need. First, you will start with installing a 4-Way wiring harness, # 118378. The tail light signals on your Tundra work on a 3-wire system. The converter takes those signals and converts them down to a 2-Wire system used by the trailer. I have included a link to the installation details for reference. Next, you will need to install a 4 and 7 Way Installation Kit, # ETBC7....
    view full answer...

  • Will Tow Ready T-One Wiring Harness # 118378 Plug Into The Factory Plug On A 2002 Toyota Tundra
  • The T-connector plug on the Tow Ready T-One Vehicle Wiring Harness # 118378 will plug into the 11-pin factory plug located under the 2002 Toyota Tundra in the rear, close to the driver side frame rail. There is another connection that has to be made under the hood of your vehicle. You will need to move the battery and find a gray connector located between the battery and the fender. You will remove the plug in the gray connector and plug-in the trailer harness fuse holder connector...
    view full answer...

  • Can You Give Detailed Step By Step Instructions For Brake Controller Install On 2001 Toyota Tundra
  • To install a brake controller on your vehicle you will need Brake Controller 7 & 4 Way Installation Kit, part # ETBC7 and the Tow Ready Custom Fit Vehicle Wiring, part # 118378 on your 2001 Toyota Tundra. If your 2001 Toyota Tundra has an existing 4-way connector, you will not need to install part # 118378. For installation of part # 118378, start by disconnecting the negative terminal on the battery and remove the battery hold down bracket and slide the battery towards the motor....
    view full answer...

  • How Long Would it Take to Install a Tow Ready Wiring # 118378 on a 2002 Toyota Tundra SR5
  • This T-One Vehicle Wiring Harness with 4 Pole Trailer Connector, part # 118378, installs very easily. After looking at the instructions it looks like it should only take about twenty minutes or so to install this product on your 2002 Toyota Tundra SR5 Access Cab with a Lift Gate. Aside from needing access to basic tools, this product comes with everything you would need to install the # 118378. I attached installation instructions below for you to check out also. These should give...
    view full answer...

  • Parts Needed to Install a 7-Way Trailer Connector on a 2001 Toyota Tundra With Existing 4-Way
  • Your best option is to install our Universal 7-Way and 4-Way Installation Kit, part # ETBC7. There are no plug-in style 7-way trailer connectors that will replace the Tow Ready harness on your truck, but the ETBC7 will use your existing 4-way and provide the additional hardware and wiring needed to have a fully functioning 7-way trailer connector. I attached an installation video on a 2002 Toyota Tundra to give you an idea of what will be involved with the installation. The installation...
    view full answer...

  • How to Install a Brake Controller in a 2002 Toyota Tundra
  • I have a way for you to install either a P2 Brake Controller part # 90885 or a P3 # 90195 in your 2002 Toyota Tundra but there isn't a plug-in adapter available that would work. You will need to hardwire the controller in. Since you do not have a factory trailer wiring you will need to start with a 4-way (if you do not have one). For that you would want the # 118378. 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...
    view full answer...

  • Does the Tow Ready Harness # 118378 Ground Separately or Through the Converter Box Harness
  • There isn't a dedicated ground wire that needs to be ran to install the # 118378 harness you referenced. It grounds through the connection that the harness with the converter box is attached to. You only need to make that connection and then connect the other included harness to the positive post on your battery and it will be fully functional. I attached installation instructions and an install video for more info.
    view full answer...

  • Transferring Prodigy P2 # 90885 Brake Controller from Ford Explorer to Toyota Tundra
  • Since trailer brake controllers are not vehicle-specific you can indeed transfer your Tekonsha Prodigy P2 # 90885 from your Ford Explorer to your 2001 Toyota Tundra. You will need the trailer brake install kit # ETBC7 that you referenced. If your Tundra does not already have a working 4-pole flat trailer connector at the rear bumper you will first need to install one. There are both hard-wire types (cutting and splicing required) and custom-fit plug-in types, which is what I suggest....
    view full answer...

  • Wiring Up Third Brake Light for Truck Bed Camper Shell
  • Sounds like you are trying to wire up the third brake light of a camper shell. The tow package wiring will not work because the turn signals and brake light circuits are on the same wire. You could use the third brake light at the top of the cap (if equipped) and tap into the brake light there by removing the light to access its wiring. Or you could use a fuse tap and tap the stoplights and high mounted stoplight Fuse - Position 29 - 15amp located in instrument panel fuse block. And...
    view full answer...

  • Adding a 7-Way Trailer Connector and Brake Controller on a 2002 Toyota Tundra
  • Universal trailer wiring harness with brake controller harness # 22550 is a universal fit type of item so there are no vehicle specific installation instructions. I have included a link to the instructions that it does have for you. Another option is to install a 4-Way first, # 118378, on your 2002 Toyota Tundra. Then you can install 4 and 7-Way installation kit # ETBC7 which will allow you to hardwire in a brake controller. I have included some links that explain and show the ETBC7...
    view full answer...

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

Info for this part was:

Test Fit:
Joe V

Video Edited:
Zack K

Expert Research:
Sarah L

Expert Research:
Robert G

Expert Research:
Michael H

Expert Research:
Jeff D

Expert Research:
Jameson C

Video Edited:
Joshua S

Test Fit:
Nicholas E

Updated by:
Laura H

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