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Curt Circuit Protected Converter w/ SMT

Curt Circuit Protected Converter w/ SMT

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Trailer Wiring

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Install a 4-way trailer connector on your vehicle with this wiring harness with tail light converter. Harness splices into existing wiring. SMT construction ensures superior performance. Lowest Prices for the best trailer wiring from CURT. Curt Circuit Protected Converter w/ SMT part number C56175 can be ordered online at or call 1-636-306-4830 for expert service.
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  • Reviews (305)
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CURT Trailer Wiring

  • Trailer Connectors
  • Vehicle End Connector
  • 4 Flat
  • Plug and Lead
  • CURT

Install a 4-way trailer connector on your vehicle with this wiring harness with tail light converter. Harness splices into existing wiring. SMT construction ensures superior performance.


  • Provides a 4-pole flat trailer connector for the vehicle
    • Compatible with 5-pole, 6-pole and 7-pole adapters (sold separately)
  • Hardwires to existing harness behind tail lights
  • Solid one piece construction
  • 16 Gauge bonded wire with 4-flat plug
  • Factory appearance
  • Simple do-it-yourself instructions on every package
  • Not recommended for vehicles with LED lights


  • Wire configuration:
    • Red: brake lights
    • Yellow: left turn lights
    • Green: right turn lights
    • Brown: Tail lights
    • White: ground
  • Wire gauge: 18
  • 1-Year limited warranty

Tech Tip: It is always a good idea to apply a small amount of grease to all electrical connections to help prevent corrosion.

Warning: Overloading circuit can cause fires. Do not exceed lower of towing manufacturer rating or:

  • Max. stop/turn light: (3 amps)
  • Max. tail lights: (7.5 amps)

Read vehicle owner's manual and instruction sheet for additional information.

Surface Mount Technology (SMT) is a method for constructing electrical circuits where components are mounted onto the surface of printed circuit boards.

56175 CURT Vehicle Wiring Harness - 4 Wire

Item # C56175

Installation Details C56175 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Reviews

Curt Circuit Protected Converter w/ SMT - C56175

Average Customer Rating:  4.7 out of 5 stars   (305 Customer Reviews)

Install a 4-way trailer connector on your vehicle with this wiring harness with tail light converter. Harness splices into existing wiring. SMT construction ensures superior performance.

2004 Volkswagen Jetta

I've been using this wiring harness for around a year now and it's performed amazingly. I have a 2004 VW Jetta Wagon, picked up some cheap female "pin" connectors as my taillights on my car had pins that you could just slide a connector on to. I was able to use this method to install this harness without actually cutting into any of my cars wiring. Working amazingly.

Still working great 2 years after purchase. No complaints at all.
Corey - 05/06/2022


I bought this kit for my 1994 Jeep Cherokee XJ and while it seemed like a good purchase at the time, unfortunately after installing it myself found issues with it. Driving lights on the trailer worked as they should, left and right blinker were extremely dim as were the brake lights. I tried a friends trailer and had exactly the same issue. Used a multimeter to check for correct voltage and continuity, everything seemed to check out fine. Problem persisted even after taking it to an auto electrician, so after about a month of trouble shooting and spending more money than I wanted to in diagnosis I ended up buying another 'plug and play' from a local auto parts store and after installing that one myself all the problems I had before vanished.

I will have our Customer Service team reach out to you. It is possible that the ground also needed to be checked. We do have a FAQ that helps with trouble shooting.
-- Etrailer Expert Jenny N - 04/07/2022


eTrailer gets a grade of A+. The actual part gets a grade of B-. Two of the wires arrived slightly damaged - luckily near the cut end so I didn't have to lose much length. The sticker identifying the 4 wires on one side and 5 wires on the other was upside down, so I peeled it off and reapplied (my OCD kicking in!). I wanted to keep my original quick release plugs on 1996 Jeep Cherokee Sport & was able to do that. Used heat shrink connectors between them & Curt Converter. All lights on vehicle & trailer working perfectly again!


Nice kit, worked great for a month. Now it doesn't turn the brake lights or tail lights.

A common cause for this type of issue is a bad ground connection or bad wiring connection. You will want to make sure all connections are secure and make sure your ground is at a direct, clean, and secure point.
-- Etrailer Expert Brooke M - 04/27/2022


The instructions were clear as well as the label on the converter box. My only issue was the ground screw and recommended size hole did not result in a snug connection to ground (which would compromise the entire system). I found a larger sheet metal screw and resolved the problem (on a whole, this was not a big deal); just make sure you ground screw is snug.

2009 Toyota Yaris

I got this for my 2009 Yaris. Works great to pull my Kayak trailer. Installation was pretty easy also.


Easy enough to install, I would have liked a little bit more wire on the vehicle side of wiring. Not a huge fan of splice clips, but not enough to provide my own, would like better proper crush and heatshink splicing. Just installed, so no comment of longevity or reliability.

1991 Toyota 4Runner

Works with my 1991 Toyota 4Runner.


Its average. Insulation on wires is poor. Wires not copper.


It was not as easy as the plug and play units I’ve installed on other cars. It occasionally causes turn signal function issues but seems to work most of the time.

2003 Volkswagen Golf

the day got delivered on my front porch half of it was sticking out all beat up. The side that was hanging out of the box got the finish chipped off and a little scratched


Works as advertised.


The quick splice were a bit oversized for my Audi wiring. Required me to wiggle it a bit to get a good connection to the, my guess 22ga, wire. Could also use at least a few more zipties. Otherwise, this is a good kit.

1996 Jeep Cherokee

Something is defective with this unit. While the running light circuit is fine, the circuits that convert the brake and turn signals into a single circuit (the essence of the device) is intermittent; sometimes it works properly, sometime only the left light responds, sometime only the right, sometimes nothing. I believe the problem is due to a bad diode in the unit. I am experienced with these devices, so it is not an installation error. Due to the installation, I am unable to return the unit in unused condition.
1996 Jeep Cherokee.
FYI- this unit was purchased to replace a similar unit that started having a different problem after ten years of use.

When a wiring harness is acting up, the first thing youll want to do is isolate the cause to the vehicle or the trailer wiring. Use a standard incandescent circuit tester like our part 40376 on each pin of the trailer connector as each function is activated. If youre not getting signal on the trailer connector pins, try testing on the input side of the converter. If the signal is entering but exiting the converter box, youll have confirmed that the converter is bad. Youll also want to ensure that the ground connection is secure. An insufficient ground can cause all kinds of odd behavior in the lighting. Ill link you to an help article on trailer wiring troubleshooting.
-- Etrailer Expert Mike L - 10/10/2018

2005 Hyundai Elantra

OK this product is great, installs quickly with the supplied tap connectors and works as expected. i installed on a 05 Hyundai Elantra.
Do yourself a favor and save yourself hours of troubleshooting. take some sandpaper and scratch off the paint on the metal surface of the car. I did it inside the light access panel. Use the supplied self tapping screw to make a Solid ground or your trailer lights will not work! i took a shortcut and secured to a screw in the panel, with paint under it. While this was sufficient ground for my test light, it was not for the trailer lights. <- this really threw me off and i wasted a lot of time troubleshooting. i even thought my trailer lights were bad and got a replacement set! but no good until i grounded properly.
PS tech support was AWESOME! i had to call twice, once for the hitch install, another for trailer light issue. they answered my questions quickly and even helped me troubleshooting my trailer light issue!.
When it comes time to get a hitch for my wife's van, i am definitely re-ordering from


One seller that I saw online said this is not right for my vehicle. I will not be using it until I am sure


Fit my car and easy to install and good instructions included well made would buy again.

2003 Saturn LW300

The trailer wiring adapter worked fine on my 2003 Saturn LW300. The unit construction was excellent. I did have to spend a while finding the proper wires in areas that were practical to splice in and had to do a lot of "pinning" with a voltmeter to determine which wire carries the correct signal.
This may be difficult for someone with little experience in wiring. Most connections were made in the spare tire compartment with one behind the right tail light, all within the vehicle.
Overall I am very satisfied with the product.


Pretty straight forward install and made easy with quick connects

1999 Toyota Tacoma

Good price, product was perfect, and the shipping was quick. Problem solved. T-taps are sort of miserable, but that's on the installer, not the product - cutting, soldering, and heat shrinking is definitely the way to go.

If you have a problem with your 'Yota truck lighting acting wonky, chances are very high this unit is your issue! Mount it up high, on the bottom of the bed to keep it dry and give it decent life. The harness cover is a nice touch that does not come with all of these - pack it with dielectric grease, and you'll get many years out of this.

Good job, etrailer!

We have seen some wonky trailer light issues with Toyotas when adding aftermarket harnesses like this. Typically the issue is the ground. The Toyota frames do not ground as easily as other makes. Sometimes we have to move the ground or extend it to a factory ground point in order for the system to function correctly.
-- Etrailer Expert Patrick B - 03/04/2013

1998 Volkswagen Beetle

The Circuit Protected Converter # SMT C56175 trailer lighting harness for my 1998 VW Beetle arrived within a few days and was easy to install with the include instructions!

All trailer lights worked perfect the first time they were checked after the install! Great job to ALL of you at

From the day I installed the SMT C56175 Converter, I have had no problems at all! This is a well designed, high quality item that I would highly recommend to anyone!This item still gets a five star rating all day long!All The Best,David W
David W - 01/04/2015

1999 Oldsmobile Intrigue

Fairly easy to attach just had to double check the wiring on the car and had to sandpaper away some paint in order to get a good ground connection.

2004 Saturn Vue

Was very happy and satisfied with my purchase and delivery of my product. Insulation went very well.


great wire harness, could not have been easier for the "common man" to deal with ! came with the hitch, I paid for it, but same package so didn't have to wait for a second box.

Darrell N - 06/17/2015


I installed this on my motorcycle, a 2004 Honda VTX 1300S. The converter itself is attached beside the license plate, exposed to the weather. It has functioned flawlessly for almost a year now, through Kansas cloudburst, desert heat and mountain freeze. If I should ever need another (not likely), I will get the same model.

A year later and it still works just fine.
Alan - 11/27/2019

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