bing tracking image
  1. Electrical Tools
  2. CURT
  3. Testers
  4. Tow Function Tester
  5. Black
Curt LED 4-Way Flat Connector (Vehicle End) Tester

Curt LED 4-Way Flat Connector (Vehicle End) Tester

Item # I26
Our Price: $4.75
You Save: 74%
Electrical Tools
Shipping Weight: 0.02 lbs
Add to cart
zoom in icon
slider vertical icon
zoom out icon
Comment field cannot be left empty.
Name field cannot be left empty.

Thank you! Your comment has been submitted successfully. You should be able to view your question/comment here within a few days.

Error submitting comment. Please try again momentarily.

Product Images

In Use/Installed

Customer Photos

Need help with installation?
Locate installers near me
1-800-940-8924 to order CURT electrical tools part number I26 or order online at Free expert support on all CURT products. Great prices and Fastest Shipping for Curt LED 4-Way Flat Connector (Vehicle End) Tester. Electrical Tools reviews from real customers.
  • All Info
  • Reviews (1409)
  • Q & A (0)
  • Videos (2)
  • Photos

CURT Electrical Tools - I26

  • Testers
  • Tow Function Tester
  • CURT
  • Black

Curt LED 4-Way Flat Connector Tester

This circuit tester plugs into the four-way trailer connector on the vehicle. The bright LED lights analyze the trailer connections and indicate which functions (tail, left turn and stop, right turn and stop) are working properly and which are not.

58260 Curt LED 4-Way Flat Connector (Vehicle End) Tester

Video of Curt LED 4-Way Flat Connector (Vehicle End) Tester

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

Video Transcript for Curt LED 4-Way Flat Connector Vehicle End Tester Review

Hey everybody, Ryan here at etrailer. Today, we're going to be taking a look at the Curt four-pole vehicle side trailer, wiring tester. So, if you guys have ever towed a trailer before I'm sure you have encountered this problem. You get all hooked up, and kind of do a walk around, you know you kind of do a pre-trip before you hit the road. You check a few things out, one of them being the lights. And, of course, you turn your blinkers on.

Maybe you have a light out at the trailer. You hit the brakes or the tail lights and something's wrong. And then this kind of turns into a headache. You know, you're, you're checking your vehicle side, checking fuses, making sure everything's good there. Then, you get the going on the trailer side.

It's kind of just a big mess. And one thing you can do to isolate that problem is use a vehicle side tester like this. So, the way this is going to work, is it's going to plug into your vehicles four way flat connector. All right, and then that's going to isolate the problem. So, once you plug this in, you can run through all of your signals and your lighting functions.

And if they all work back here, then you know, okay something's going on with my trailer and you can focus your time on that. If you don't have all your functions back here chances are good. You could say, okay, trailer's probably okay. I probably have an issue with my vehicle side and you can focus your energy there. So, at the end of the day, if you do have an issue, it's a great little tool that can potentially save you a ton of energy.

So, whenever you are plugged in to your vehicle side, you can test the function. So we're going to have our left turn signal, our right turn signal, our taillights, and our brakes. So, since these lights are LEDs, really easy to see, even on a sunny day like today, which is convenient, especially if you're by yourself, kind of trying to, you know if you have miring stored inside you can hold it up or mount it up and check it while you're in the driver's seat, so you ain't got to get out of the car every time. But, since we don't have any labels or anything here, I figured it'd be useful to share what lighting function illuminates the light on the test, or if that makes sense. So, this light here should turn on when you use your right turn signal, the one next to it should turn on when you use your left turn signal, both of these lights should illuminate when you apply the brakes, and this one should come on whenever you have on your tail lights. So, let's say if you're, you know, testing your, your right turn signal, this one should be flashing. See, this one isn't, but this one is, okay So, you're still getting something to happen, but on the wrong circuit. So, that could help kind of direct you as well to get it figured out. You may have a short or something like that in the electrical system, and that could be looked at. So, when it comes to this tester, honestly, this is probably the last one you'll ever need, unless you lose it or something like that. Things are actually pretty, pretty stout. They're pretty solid. These are actually the exact ones we use here at the shop. And we use them day in and day out, all the time, and we've had them for years. They still work like they should every day and they really take a beating, and they just continue to work. So, for the average person to use them, occasionally, I mean this should last for the life of your vehicle or the life of your trailer, and then some. So, really nice, you know, it does have a key ring holder on the top there. And what we do, here at the shop, is usually put a zip tie or some type of key chain on there just to make a little larger so we can hang it up. If I had, you know, if I was going to keep one in my personal vehicle, something like that, you know, I'd probably end up using a key chain with my trailer lock and everything else on it, throw it in the glove box, so you always have it. So, it's a little nice touch and something I thought was worth mentioning. So, as I mentioned, this could work for your four way flat type connectors and it just plugs right in, just how you'd plug into the trailer side. And if you have multiple vehicles or different trailers, things like that and you need a different type of tester, not a big deal. We offer other ones as well. Whether you have a five way or a round seven-pole something like that. There's going to be a tester similar to this available here. That way you can use it for that wiring as well. And that'll finish up our look at of the Curt four way flat trailer, wiring tester..

Customer Satisfaction Score:

Customer Reviews

Curt LED 4-Way Flat Connector (Vehicle End) Tester - I26

Average Customer Rating:  4.8 out of 5 stars   (1407 Customer Reviews)


Very handy and works great! A super easy way to check that the wires were connected and installed properly. Be careful not to lose it since it's so small. I've got a 2016 subaru outback. In the video you can see I'm testing the brakes twice, then the blinkers, then the headlights. Super awesome little tool!




I have purchased several items from etrailer in the past. Most recently, for my 2018 Jeep Wrangler. I installed the hitch, mounting bracket and wiring. All worked perfectly and the instructional videos and on line support are outstanding. I only think of etrailer when looking for trailer equipment. Thank you.


Makes testing the electrical connections easy


I really don't think I needed this for a new install but now I have one to eliminate the vehicle as a electrical problem when trouble shooting wiring going to a trailer. I did test my Flat connector after installing a wiring harness from Curt.


There aren't any instructions with this. I plugged it in and could figure it out by turning on: left turn, right turn, push brakes, flashers, headlights, but would be helpful to have something just telling you how it's *expected* to behave.


Workers great, easy way to ensure you installed wires properly. And to make sure they are working before a trip.


Nice little inexpensive test plug to have around to confirm a tow vehicle's 4-way trailer hitch wiring.


The Draw-Time trailer hitch went on without a "hitch". The process of ordering the correct components (hitch, wiring harness and 4 pole plug mount) for my 2016 Ford Flex was nearly effortless with only one call to clear up one concern. etrailer's videos that were vehicle and product specific made for a great experience. Thanks


Inexpensive tool to confirm installation and troubleshoot before hooking up to a trailer.


The four way connector tester works excellent with my newly installed trailer wiring. I used the tester as soon as I installed the wiring and it worked right away. Eliminates the question as to whether the system is working right. Thank you!!


easy to troubleshoot trailer to truck wiring issues with this simple tester


This makes it alot easier to check the car side of flat four connectors.


Just got this couple hours ago and haven't even started working on it but if it's like everything else I've gotten from each trailer it's going to be wonderful thank you e-trailer for all three items


This wiring harness tester works well but has no labels for what the leds are showing. It is a good indicator that power is getting through and final test should be done using a trailer to verify absolute correct wiring.


Helped my verify connections without having to hook up the trailer.



Works as expected with no issues.


Pretty easy to install with the instructions correct. Have not had the opportunity to try it out on a trailer yet (change of plans).

Bette F.


Works fine


An added extra to my purchase of hitch, wiring harness and e-bike rack from E-trailer. Anyone needing equipment for their vehicle should contact E-Trailer for any necessary parts for their towing needs.


Drove from San Diego to Alaska - smooth ride w/trailer...


Adds peace of mind to the wiring installation. I was quickly able to validate that the wiring kit worked properly.


It works and the lights are pretty... Bottom line, it works.


Nice to have, helps verify you wired it correctly, without hooking the trailer up.


Works great for checking trailer wiring!


Bought my 2014 Edge new with a hitch but no wiring harness (bike rack only). Over time came to realize I could really use the wiring harness. Did an Internet search, etrailer came up, found the harness I wanted, the video was the clincher for me. I'm a DIY'er but not so much on cars. Followed the video instructions, even bought the silicon sealer and tester. I ran the battery wire under the car and this was the only challenge for me as I do not have a lift, so laying on my back on a cold winter day took a bit longer than expected. Product delivery was prompt, fair price, very happy with this purchase.


it does what it is supposed to do, but the indicator lights are not well identified on the tester and so are much harder than necessary to interpret

Show More Reviews

See what our Experts say about this CURT Electrical Tools

  • Which Lights will Illuminate on the Tester # I26 When Brakes are Applied
    When your brake lights are pressed and you are using the # I26 as a tester the two pins opposite of the jacketed (ground) pin will illuminate. These are the left and right turn/brake light circuits.
    view full answer...
    Image 1 for
  • Why Would Circuits of the I26 Partially Glow When No Trailer Wiring Circuits are Activated
    It sounds like your trailer wiring setup is fine. The thing about LEDs (like what the # I26 has), is that they require such a tiny amount of amperage to partially illuminate that when they are used in trailer wiring situations they can partially glow like you described if there is any amperage at all bleeding out of the circuit. What I would do is connect the 4-way of your 2014 Ford Explorer up to a trailer and see if it functions properly. If it checks out then you would be good to go.
    view full answer...
  • What are the Different Circuits on a 4-Way
    The jacketed circuit is the ground. The one right next to that one is the tail light circuit, next to that one is the left turn circuit. And then the last one on the end is the right turn circuit. Check out the picture I attached to see the circuits labeled. I attached an FAQ article on trailer wiring that you might find informative also.
    view full answer...
    Image 1 for
  • What are the Functions of the Lights for Trailer Wiring 4 Pole Flat LED Tester # I26
    From left to right the first light tests running lights, the middle light tests left turn and brake lights, and the last light tests right turn and brake lights. On a 4-Way flat vehicle connector, the one exposed pin is the ground, next to that is running lights, then left turn and brake, and the last pin is right turn and brake.
    view full answer...
    Image 1 for
  • No Trailer Lights on a 2018 Honda Pilot with Tekonsha 7-Way Harness Part # 118760
    What type of tester are you using? If it is one like the Curt LED 4-Way Flat Connector part # I26 then that may be part of the problem as these are not foolproof and do not always work with all wiring harnesses. Therefore, I would check each of the pins with an actual circuit tester while the respective signals are active. These are much more accurate than the above testers. In regards to the T-One Vehicle Wiring Harness part # 118760 which is a fit for your 2018 Honda Pilot, there are...
    view full answer...
  • Availability of Curt 4-Way Circuit Tester I26
    We do have the tester you are looking for with the # I26. I think the confusion is that the part number is not 126 as its I26.
    view full answer...
  • Can Curt LED 4-Way Flat Connector # I26 be Left on Vehicle Indefinetely
    Leaving the Curt LED 4-Way Flat Connector # I26 plugged into a 4-way for an extended period of time would not be an issue at all. Since you used dielectric grease like the part # 11755 you wouldn't have to worry about corrosion either.
    view full answer...
  • How to Get Replacement Mounting Hardware for a Curt Trailer Hitch
    The square hole 1/2" washers you're referring too can be found in the replacement hardware kit # RHK. You'll just need to enter your hitch part number in the "Hitch Item Number" and we will send you an everything for an entire replacement kit, including the square washers.
    view full answer...
  • Troubleshooting Vehicle-Side Trailer Connector Right Turn Signal Staying On
    If you are putting a test light like the Curt # I26 on your vehicle-side 4-Way then you may have installed your vehicle-side 4-Way incorrectly. Is your running light indicator blinking when you put your right turn signal on? If this is the case then you simply need to swap out the wires for your right hand and running lights (see attached photo). Another possibility is that you have a bad ground or your vehicle connector is full of corrosion. Check both of these while you are at it and...
    view full answer...
    Image 1 for
  • Testing the Hopkins 4-Way Connector Not Showing Power on a 2009 Chevrolet Equinox
    You can test the Hopkins # HM11141265 by using a circuit tester like part # I26 while you have a helper activate the various light functions on your 2009 Chevrolet Equinox to make sure that the correct signals are coming through. If they aren't then you have some bad wiring on your Equinox (granted you installed the fuses and relays and they are okay). If you do get signals then you have a wiring issue on your trailer. This can be traced back to a faulty ground or damaged wiring. Make...
    view full answer...
  • Can I Get A Standalone Curt Wiring Converter For My 2017 Toyota Highlander
    I did some research and I checked the Curt website to see if you can get the converter for your 2017 Toyota Highlander separately. You will have to get the Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector, part # C56217, to get this converter. I have included a product description link and a video of this part being installed on a 2017 Toyota Highlander below.
    view full answer...
  • Installation Video Reference for Universal Trailer Wiring on a 2013 Volkswagen GTI
    The (discontinued) Tekonsha Powered Tail Light Converter 119190KIT is a universal wiring harness so there aren't any specific instructions when it comes to installing the kit on your 2013 Volkswagen GTI. With that being said, we did get the opportunity to install the Curt alternative, part # C59236, on a 2016 Volkswagen GTI and we got a video on this. I'm linking that video to this answer page for your reference since these wiring kits install in the same manner. Please note you'll need...
    view full answer...
  • Troubleshooting Left Side Tail Light Not Working on Trailer With 2017 Infiniti QX60
    The blinking on the # I26 is actually correct. It doesn't make sense that the right turn signal blinks on the left and the left blinks to the right of the right turn signal light (it even sounds confusing) but that is how it's designed. You can see this in our review video below. Based on the fact that this is working correctly it could still be the trailer side. Take a circuit tester like the # PTW2993 and check to see if you have power right behind the trailer side connector. If you...
    view full answer...
  • How to Wire LED Replacement Trailer Lights
    If you are looking at and LED Trailer Tail Light like part # STL8RB, then you will not need a converter to make it compatible with the 4-Way Wiring Harness on your truck. You will need to figure out the wiring on your trailer to make sure that you get all of the wiring done correctly. You can use a Circuit Tester # I26 for that purpose. All you have to do is hook up your new LED lights using the following information. Brown is for tail lights Green is for stop and turn White is for ground The...
    view full answer...
  • Malfunction Turn Signal Light on Sunline Travel Trailer
    The first step would be to check the wiring from the malfunctioning light all the way up to the connector. Make sure all the connections are reasonably clean and secure, and check for frayed wires. If everything looks good from there, I would begin to look at the tow vehicle wiring. Check to make sure your connections are clean and secure. We have a few handy devices that could help you check all this. You could use a circuit tester like part # PTW2993 to check to see what connections...
    view full answer...
  • Will Wiring Harness # C56331 Work with Power Lead Disconnected or Damaged?
    The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56331 will not function without the power lead. It may function with a slightly damaged power lead, so I recommend using a tester like # I26 to test your wiring functions and simply visually inspect your power wire to your battery.
    view full answer...
  • Vehicle Side 4-Way Trailer Connector Plug-in Circuit Tester Lights Light Up when Connected
    If the lights on a 4-Way trailer connector tester such as # I26 light up when connected that means that those circuits are receiving power. It doesn't take much power to light up these small LED lights so even residual current could set them off. This is typically more likely on aftermarket installed trailer wiring harnesses that have a connection to the battery to power the trailer lights. It could also indicate a short circuit if the lights stay on all the time. The likely cause is a...
    view full answer...
  • Availability of 4-Way Tester and Connector Cover
    We do have 4-way testers that would plug into the car side of trailer wiring with the part # I26. This has lights that will come on when it detects that a circuit is active. We have the dust cover part # C58200 which is a fit for both the trailer and vehicle side 4-ways of a vehicle. This would work well for you. I attached a help article on troubleshooting trailer wiring for you to check out too.
    view full answer...
  • Is There a Way to Trick Parktronic Sensors on a 2016 Mercedes-Benz Sprinter for a Bike Rack
    I am not sure if this will have enough draw but we have testers like the Curt LED Tester # I26 which puts a small load on a 4-Way Flat connector. This is used to make sure that your wiring is working correctly but it may be enough to trick your sensors. If you have a 7-Way then I recommend using the Tow Ready # 20142 as it will simulate a draw as well. Please note that both of these products are designed to be plugged in for short periods of time and haven't been tested for prolonged...
    view full answer...
  • Trailer Hitch and Wiring Recommendation for 2014 Toyota RAV4
    For a trailer hitch for your 2014 Toyota RAV4 we have the etrailer hitch part # e99864 that you referenced which is a confirmed fit and would work well. This would have been what I would have recommended you since it has great capacities and price so you are on the right track. Then for trailer wiring the Tekonsha kit part # 118578 that you referenced is the best choice as it is the most reliable option we offer too so it's the way to go. To test this 4-way we have the # I26 that you referenced...
    view full answer...
  • How to Determine if a 2017 Toyota Highlander has a Factory Tow Package
    To determine if a 2017 Toyota HIghlander has a factory towing harness, start by opening up the rear hatch. Then, lift up on the rear compartment panel and pull it out. Remove the two driver-side panels by pulling up on them. There, you may see a factory 4-pole. If you do, then you know for sure you have the factory towing harness. If you do not, you may still have one that didn't come with the 4-pole connector so continue to the next steps. Pull up on the tabs connecting the floor covering...
    view full answer...
  • Fuse Blows on 4-Way Harness When Using Circuit Tester 2013 Jeep Compass
    It sounds like the 4-way tester you are using like part # I26 has a short somewhere which is in turn causing the 10-amp fuse on the Curt T-Connector Vehicle Wiring Harness part # C56344 for your 2013 Jeep Compass to blow. What I recommend doing is testing each circuit with a standard test light like part # PTW2993 to check for function. If all is good, then you know the problem was in the 4-way tester you are using. All of the converter boxes used in Curt's wiring harnesses are tested...
    view full answer...
  • Comprehensive Vehicle Side Trailer Connector and Wiring Tester
    Most of the vehicle end trailer connectors we have will test for voltage on the circuits. If there was a short to ground then all of the lights would light up on the tester and you would know there is a problem. We do have a comprehensive trailer side tester, # 8010, which goes much further than any of the regular testers like # I26. But it is not designed for the vehicle side. For the vehicle side we have # HM50918 that can test multiple connector types on a vehicle (4-Flat, 6-Way round,...
    view full answer...
  • Is Dealer Activation Required for Trailer Wiring Harness # C55384 on 2015 Jeep Grand Cherokee
    When you install the Curt T-Connector Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector # C55384, it may be necessary to see a local Jeep dealer to activate the tow package wiring circuit. Some vehicles have the active tow package wiring and others do not, so you will know as soon as it is installed if this is required or not. If you test the function using a tester like # I26, a circuit tester like # PTW2993, or connect it to a trailer, you will be able to...
    view full answer...

< Previous

Do you have a question about this Electrical Tool?

Info for this part was:

Employee Joe V
Test Fit:
Joe V
Employee Andrew K
Video by:
Andrew K
Employee Joshua S
Video by:
Joshua S
Employee Jameson C
Expert Research:
Jameson C
Employee Jacob T
Video Edited:
Jacob T
Employee Chris R
Video Edited:
Chris R
Employee Cole B
Installed by:
Cole B
Employee Ryan G
Installed by:
Ryan G
Employee Wilson B
Updated by:
Wilson B
Employee Kristina F
Updated by:
Kristina F
Employee Isabelle B
Updated by:
Isabelle B

At we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.

Product Experts Available Now!
Call 1-800-940-8924