Electronic controller activates electric trailer brakes with a preset intensity when you apply the brakes in your vehicle. Power output and braking aggressiveness are easily adjustable. Includes easy-to-read digital display and manual override. Call 800-298-8924 to order Curt brake controller part number C51120 or order online at etrailer.com. Free expert support on all Curt products. Guaranteed Lowest Price and Fastest Shipping for Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed. Brake Controller reviews from real customers.
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Price: $38.88

Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed

Item # C51120

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In Use/Installed

for 2008 Chevrolet Silverado 2Curt
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  • Time Delayed Controller
  • Curt
  • Electric
  • 2 - 8 Brakes
  • Automatic Leveling
  • 360 Degrees
  • Vehicle Mount
  • Digital Display

Curt Brake Controller - C51120

Electronic controller activates electric trailer brakes with a preset intensity when you apply the brakes in your vehicle. Power output and braking aggressiveness are easily adjustable. Includes easy-to-read digital display and manual override.


  • Brake controller activates trailer brakes with preset intensity
    • Signal is sent to trailer brakes when tow vehicle's brakes are activated
  • Adjustable, thumbwheel power output control lets you determine the amount of braking force
    • Set to maximum when you travel through hilly terrain with a fully loaded trailer
    • Back off the power output when you tow a lightweight trailer
  • Sync setting lets you adjust the aggressiveness with which the brakes are activated
    • Get full power output faster by moving slide-bar switch forward to increase activation speed
    • Achieve smoother braking by moving switch in opposite direction to supply power gradually
  • Easy-to-read digital display communicates brake force output, sync setting, and error codes
  • Self-diagnostics function monitors trailer connection and checks for shorts
  • Built-in, slide-bar manual override
  • Quick and easy installation
    • No need to mount level like proportional brake controllers
    • Mounting bracket and hardware included
    • Plug-in, vehicle-specific brake control adapter (sold separately) can be used for certain applications to reduce installation time


  • Application: trailers with up to 4 axles (8 brake assemblies)
    • Designed for use with electric brakes only
  • Limited lifetime warranty

Time-Delayed Braking

The Discovery applies your trailer's brakes when the brake pedal in your tow vehicle is engaged. Every time you apply the brakes in your vehicle, a signal is sent - via the brake switch - to the Discovery. The controller then sends power out to your trailer brakes to activate them with an intensity set by you, at a rate determined by you. Both the amount of braking power (output) and rate of application (sync) can be adjusted to suit your preference, the road conditions, type of trailer, and size of the load. To determine which levels are best for your application, you must test out your towing setup and choose what feels best.

A time-delay controller is so named because there is a delay between the time that you initially apply the brakes in your tow vehicle and the time that the controller reaches maximum power output. Unlike a proportional brake controller, which activates your trailer's brakes based on the deceleration of your tow vehicle, the Discovery sends power out in the same way, with the same gradual delay, no matter the braking situation. Although this delay always exists, it can be adjusted by changing the sync setting.

Built-In Controls for Adjustable Power

Curt Discovery Controls and Components

The above diagram shows the controls and components of the Curt Discovery trailer brake controller.

  1. Digital display
  2. Power output control
  3. Sync control
  4. Slide-bar manual override

Output Control

During the initial setup process, use the thumbwheel control on top of the Discovery to adjust the output. The output control lets you set the maximum amount of power that will be applied to your trailer's brakes. Typically, the output is only readjusted when you experience changing road conditions or if you switch over from a heavy, loaded trailer to a much lighter, empty trailer, or vice versa. To get more power to your brakes, rotate the switch to the right. To decrease the power output, move it to the left. The output setting will appear on the digital display when you press the brake pedal or activate the manual override. This setting ranges from 0 to 10, with 10 indicating maximum output.

Sync Setting

To adjust the aggressiveness of your trailer's braking action, use the slide-bar control on the side of the Discovery to change the sync setting. If you want to reach maximum power output faster, move the switch forward. To get smoother braking action, slide the switch backward, thus supplying power to the trailer brakes more gradually. You can alter the sync setting to suit your driving preferences or to improve handling based on changing road conditions or varied trailer loads. The digital display will only show the sync setting as you adjust it.

Quick, Simple Installation

Because inertia plays no role in the functioning of this controller, you do not have to mount the unit at any particular angle. As a result, mounting options are limitless, so long as you can still easily access the controller.

Installation of the Discovery requires that you either purchase a custom wiring adapter designed to plug into the controller or that you hardwire the controller directly into your vehicle. To hardwire the Discovery, you must remove the plug at the end of the integrated wiring harness.

Installation Accessories

For easier installation, a vehicle-specific wiring adapter (sold separately) is available for most newer trucks and SUVs. One end of the custom adapter plugs into your vehicle, and the other end plugs into the controller - no hardwiring required.

Note: If a custom brake control wiring adapter is not available for your vehicle, one of the following will be required:

20-Amp circuit breaker (9506P - sold separately) for 2- to 4-brake applications

30-Amp circuit breaker (38630 - sold separately) for 6- to 8-brake applications

See also etrailer.com's exclusive 7- and 4-way brake control installation kit (ETBC7 - sold separately) if you don't already have a 7-way plug at the back of your vehicle.

51120 Curt Discovery Time Delay Trailer Brake Control

C51120 Installation InstructionsInstallation Details C51120 Installation instructions

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Video of Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed

Videos are provided As a guide only. Refer To manufacturer
installation instructions And specs For complete information.

Video Transcript for Curt Brake Controller C51120 Review

Today we're going to take a look at the Curt Discovery Trailer Brake Controller number C51120. This time delayed brake controller activates trailer brakes with a preset intensity. The signal is sent to the trailer brakes when the tow vehicle's brakes are activated.It has an adjustable thumb wheel power output that allows you to determine the amount of breaking force you would set to the maximum when you travel through a more hilly terrain with a fully loaded trailer and you would back off the power output when you're towing a smaller more lightweight trailer.It also features a sink switch here on the side. It allows you to adjust the aggressiveness of the brakes. If you want it full power in this position right here. It will increase the activation speed of the brakes and you would move it back in the opposite direction to achieve a smoother braking by supplying the power more gradually.

It has an easy to read digital display that communicates brake force output, sink setting and air codes and we'll attach this to a power supply in just a moment so you can see that a little better. Self-diagnostics function monitors the trailer connection and checks for shorts. It has a built in slide bar emergency manual override and again we'll discuss that more in just a moment. It has also has a quick and easy installation. It comes with the mounting bracket right here.

The screws to attach the bracket to the controller as well as a quick reference card if you have any questions. One of the differences between the time delay brake controller and a proportional brake controller is there's no need to mount this one level the way you would a proportional controller.You can mount it up, down, side to side, as long as you can see the digital display you're good to go. This application is for trailers up to four axles or eight brake assemblies. It's designed for use with electric brakes only and it does have a limited lifetime warranty. Now we're going to attach it to our power supply and the wiring harness that we're using here is the Curt Universal Wiring Adapter for Curt Trailer Brake Controllers, number C51515.

This particular harness ends in a pigtail and it is intended for vehicles who do not come with a factory installed brake controller port. Now when you hit the brake you will be able to see the digital display and say right here we'll use our output knob here. You can go from zero to ten and we'll set that at five for right now and over here our sink all the way to nine and then slide it back to zero. We will put that at five as well. When we talk about our emergency manual override say youre in traffic and somebody cuts you off and you have to hit the brakes really quick what you would do is hitch your emergency manual override and instead of the normal amount of time it would take for the trailer brakes to brake this removes the time delay function and the maximum output that you had preset it goes to the brakes immediately to help slow you down to prevent any accidents.

That should just about do it for our Curt Discovery Trailer Brake Controller number C51120.

Customer Reviews

Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed - C51120

Average Customer Rating:  4.9 out of 5 stars   (139 Customer Reviews)

Electronic controller activates electric trailer brakes with a preset intensity when you apply the brakes in your vehicle. Power output and braking aggressiveness are easily adjustable. Includes easy-to-read digital display and manual override.

- C51120

by: Bob R02/05/2016

I bought a new car dolly with electric brakes to pull with our motorhome ( Fleetwood FlAIR 2001 ) as all states require brakes on trailers at all different weight levels. I called E trailer and spoke with Danna and after talking with her about different models I choose the C51120 time delay control, as it can be adjusted to work well with the tow vehicle . I received the control with in 3 days of the order and went to put it in and found under the dash wire a harness by Fleetwood which told where each wire on the controller went on the harness. I was able to hook it up sitting in the drivers seat. Completed the hook up and started to test the operation, to find I was not getting the proper readings. I talked with Tom and he said he would bench test a like control and report back to me, at 6 pm he left a message on our phone that he believed the problem was along the blue wire to the trailer on the tow vehicle . I started at the back of the, motorhome and moved forward testing for a brake signal, I found that the butt connector had pulled apart and was not getting current to the plug in at rear of coach. Hooked it back together and re taped the wires and it works like a charm. I want to thank all off you for the prompt and knowledgeable service, I would recommend E trailer to anyone who wants to deal with a great staff and company Thank you 237064


I used this controller to pull ma car dolly to AZ and back through all the mountains and it worked GREAT I am very happy with how it worked Great product

Bob R - 02/04/2017


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by: George D10/17/2015

the brake controller with all the wiring plus the 7 pin plug was better than i thought . it even has great instructions and easy to read. the price was good . the 7 pin plug even has the 4 pin connector mounted in with it very glad that i bought it is everything that you need to make it work . everything about it is excellent very glad that i found it here at a good price . even fast shipping . again thanks for good product 230172


Use it for pulling camper works great even a good price fast shipping . Its been a year and still working great.

George D - 10/16/2016


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by: Bobby04/30/2016

Easy to install and Thanks for the help. 247727



Bobby - 04/30/2017


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by: Randy G01/04/2014

This is an outstanding product - exactly as described. I installed it into my 2005 Ford F150 XLT Extended Cab. Took longer for me to decide where to put it than the actual installation, which took about 3 minutes. My truck had the tow package so the harness - which was included - was an exact match to my truck's harness plug on the right side of the dash in the driver's area. Extremely satisfied. 111895


It is still working well I used the Brake Controller a week ago and still no problems. Works exactly as described. Great product!

Randy G - 01/05/2015


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by: Raymond L.05/30/2015

Awesome product. Easy to install and adjust to your liking. Use in combination with the custom wiring adapter for your vehicle and you have a product that can't go wrong! 198827


This product has worked flawlessly this past year. Great product and will definitely deal with etrailer for all my trailer needs

Raymond L - 05/29/2016


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by: Mark Mason03/19/2014

I always get excellent products and advice from Etrailer will keep comming back 121339


Great I rarly have to recalibrate the brakes and my wife will now tow with confadence

Mark M - 03/19/2015


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by: J.C. from Bay City02/24/2014

Ordered a brake control and an inline circuit breaker on Feb 11th and shipped the same day. I chose the least expensive shipping option (my bad). A combination of UPS/US Post Office, or so I was told after calling to find out where my shipment was. Tracking info said delivery by the 15th. When it didn't show I called etrailer and was told the post office had it and it was out for delivery...2 days later I finally received it (Feb 20th). I ordered a hitch a couple of weeks prior and received it in 2 days. A 49lb hitch vs a 1lb (maybe) package. Not etrailers fault but I can see why the post office is going broke with service like that! 117375

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by: Adam S.06/17/2016

Trailer Brake Assist works as advertised. Installation was challenging but the how-to video and instructions helped. Hardest part was routing the wires without our 2006 Honda Pilot on a lift. Once it was installed I hooked up our trailer and took it to a large parking lot close by to test and adjust the module. I put my brakes on when we first got there and the trailer screeched to a halt, letting me know it was working well! I adjusted it to the recommended setting and it's worked great since. Makes it especially comforting coming down out of the Sierras. I highly recommend trailer.com for all your towing needs. 262275

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by: Patrick T.01/23/2014

This controller work great in my 2008 Tundra, and is very easy to set up and adjust. 114575


Still working great no problems

Patrick T - 01/23/2015


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by: Justin08/02/2016

After reading the reviews of this product I decided to give it a try myself, with a great price. When I received it within a week along with the plug and play 7 prong trailer hitch adapter, I realized I was missing something. The plug and play adapter for this product. It showed me it when I was buying and for what ever reason I didn't have the option to add it as well. It was very easy to install, like I said plug and play. The problem is it does not work. followed all the directions, double checked everything I just don't have a signal to the trailer from the break controller. Good luck 278660

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by: Patrick03/12/2017

I haven't thought about those products since the day I installed them. That's because I haven't had a reason to think about them again. They have worked perfectly since I bought them. Not only that but, your price, if I remember correctly, was as good as or better than anyone else's. Your website made my purchase easy and I can't imagine that I would buy anything that you sell from anyone else. Great product (I know your company didn't build it but,....) no hassle, quick delivery, and great service. All around good experience. Thank you for checking (great customer service). 355662

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by: Edward D07/20/2016

Bought brake controller and custom wiring harness for my 09 Dodge Ram. I've had several Curt brake controllers in other trucks with good results. For the price they are good quality controllers. I've had both delayed time and proportional controllers, both do the job. I prefer delayed time on 1/2 ton trucks since you can set the controller to have trailer brakes apply harder. Installation is very simple, decide there's you want the controller, have 2 screws to hold bracket and 2 screws to secure controller. Took about 5 minutes to install. 274320

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by: Drew V.10/10/2016

Installed the Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed - C51120 in our 1982 GMC 1-ton dually to activate the brakes on our Forest River Sandpiper Sport SP34T 34' triple axle toyhauler travel trailer... The Curt Discovery Trailer Brake Controller installed easily, adjustment was fairly painless and it performed flawlessly on a recent 600 mile trip. We would definitely recommend this product and etrailer.com! 305035

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by: Bill12/30/2013

This is a very small brake controller unit. I had to find the right spot to mount so my knees didn't bump it when I got in and out of the truck. Once the perfect spot was found, the installation was a snap. I used the correct wiring harness to make installation easy. Just snap into back of controller and then into the truck's brake controller wiring harness in the back of dash. It was the simplest install I have ever used. Thanks!!!! 111474

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by: Dustin09/18/2013

I purchased this item with the premade connection wire for my 2010 Dodge Ram with 7 way trailer wiring adapter. I had this installed in less than 12 minutes! Plug the harness in and mount it you are done! Shipping was super fast had my item in 3 days. The best part is I can remove this when I am not towing my RV so that I keep the stock appearance of my truck. Best online buying experience ever! 100495

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by: Dave C05/11/2017

The 1st brake control recommended by the associate was not compatible with my vehicle. When I called in the person I talked with discussed my problem with a tech and discovered that my vehicle needed another type. They immediately sent me the other brake control with a email to print out the return prepaid shipping label. You can not ask for better customer service 379105

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by: Rock W.07/29/2013

I chose this brake controller because it was like one I had before so no learning curve needed. Plus I didn't want to mess with extra install concerns of the proportional type controllers. With the video install tips the shade tree mechanic is back in action. With the yr/make/model suggested cable, hook up was a breeze. Ready to do some camping. Thanks etrailer 92116

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by: Tacoma Stan09/11/2016

Fit nicely under the dash on the left side. Also installed a 7/4 pin connector in the bumper, replacing the blank plug from the factory(etrailer p/n HM40975-11998) 293471

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by: Sarge05/30/2017

Simple to use and was amazing! It hooked up in maybe 15 minutes using the specific wiring harness. (That was reading the directions too) It made a huge difference. When breaking I only had to press down on the pedal 1/3 of the way to stop my camper. I didn't have the setting that high either. Great investment. I should have gotten it earlier!! 386425

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by: Loren C.06/06/2016

Super fast delivery. Product was just like advertised plugged it in and mounted it and pulled my camper that weekend and it worked perfectly. The item description was very thorough and eliminated buyer mistakes. Order process simple and secure. Definitely would use E trailer again in the future and would highly recommend them to anyone. Thanks. 258339

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by: Les F02/20/2017

Dealing with etrailer was a good experience. Shipping was great and everything I ordered was in the package. Having just received the package, I haven't installed it yet but I am sure it will be just what I need. I will certainly deal with etrailer again when the need arises. Thanks etrailer for making my shopping experience hassle free. 343758

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by: e whitestone12/03/2013

Much, Much better than the proportional type I had before. The proportional types have to be mounted level. This Curt solid-state digital never needs to be level, in fact it could be mounted upside down and still work. No problem finding a place to mount, since it doesn't have to be level. A great price at etrailer makes it that much better. 109008

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by: David C.05/17/2014

I purchased this controller for a 2006 4 horse stock trailer & a 2006 Dodge Ram 2500 pick-up truck. The installation video from etrailer was very informative & the instruction from the product was very through. I was able to attached the controller & tested it within one hour. I've towed with the trailer since then & it's working great. 131087

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by: Mike11/04/2014

Good quality brake controller for my needs and although I had some issues installing it, etrailer was right there, they helped me troubleshoot my problem and it ended up being a fuse that was not installed apparently by Honda for the ebrake. I popped the fuse in and walah the controller worked perfectly. Thanks Etrailer!! 159127

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by: Tracy W06/24/2017

Easy to install. I bought this model to replace a old one that was already in the truck but was not working. Works good 398529

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by: paul t.09/29/2016

great price and great brake controller this is the 5th or 6th time we have ordered from etrailer and we will be ordering from them again as we have had great prices and fast shipping from there products and them. thank you etrailer for keeping the prices reasonable. from --savannah`s secret gardens 301430

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by: Gar102/27/2015

Product came on time and connector was correct for my vehicle. Controller is small and blends in with vehicle interior. I like the digital readout but the adjustment range is a bit difficult to get right, hopefully I will find the sweet spot between the power and the sync. For the price I like it. 176409

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by: Dave C04/09/2014

With the factory adapter the total installation took 5 minutes including a fight with a tangled extension cord. Worked awesome. Towed a 8500lb load up and down the Appalachian range without any worries. Thanks again for the fast shipping, awesome product and great customer service. 124394

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by: Andrew12/26/2013

I just received my Curt new brake controller and Etrailer truck brake harness. The package arrived promptly - earlier than expected. The harness kit has everything I need and looks like it is well made. Can't wait to get it all installed and try it out. 111247

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by: bill mussell11/22/2016

Brake controller arrived in good time and well packaged. I highly recommend this seller. I won't be installing this for a few months but ever thing looks great. I will be using this on my 2006 ford pick up and towing my 27 ft. travel trailer.BM. 318990

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by: Erik O.08/05/2013

So far so good. Product seems well made. Installation was a breeze. 5-10 mins. Ordering was simple. My Order was upgraded to faster shipping at no additional charge! Fantastic company! Will be ordering from etrailer.com in the future! 93288

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by: Kyle c.04/09/2016

I love this brake controller. It has worked flawlessly since the day I installed it I would definitely buy this unit again. The staff was great and help me troubleshoot. I love that you can adjust it on the Fly depending on the load 243551

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by: Jared H.06/25/2013

Great product for the price. This was my first brake controller and it was very easy to setup and mount. I bought the adapter cable for my truck as well and it made it even easier. For the price you cannot go wrong with this. 86013

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by: Greg M.06/21/2016

Installed on my Dodge Ram 1500'l after work today, with the adapter it was easy as pie. This unit was out of stock when I ordered, so delivery took a little longer than usual, but I have no issues with the product. 263492

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by: Mike N.05/18/2015

Installed and worked as advertised. I would have given it an excellent rating but I think the braking adjustment wheel is a bit finicky, it takes a little finesse sometimes to get it set exactly how you want. 194052

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by: Jaime H.11/25/2016

Product is good quality, I made and error in ordering it, so I am waiting for the correct part. Service over the phone was great too! Thank you for your help in ordering the right Brake Controller Adapter. 319477

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by: Dan02/21/2016

very good kit . nothing else needed .love the 7 way plug . very well made . brake controller is very good .like the ability to bench test it before install. very happy with all material and Etrailer . 238373

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by: David G.07/07/2016

Product was delivered as scheduled. Easy installation and works great. E-trailer made it easy to order and provided outstanding customer service. Would recommend them for any trailer related needs. 268879

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by: Edward P11/09/2015

I have yet to install this item,but,if it is as complete,reliable and easy to install as other trailer electrical hitch items I have purchased from Curt then I will be satisfied.Thanks Ed. 231637

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by: noah r07/20/2017

Works awesome hooked right into my truck it took longer putting the screws in than it did anything else. Very happy and stops trailer with ease. just what i needed for the heavy loads. 410152

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by: David Williams02/05/2014

I was able to install the brake control in about 15 minutes using the wiring adapter that matched my truck. Have not had a chance as of yet to try out the controller pulling my trailer. 115860

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by: Ed D.08/05/2014

Installed controller and connected trailer. Paired with the mating factory connector cable, everything was installed and working in 20 minutes. Controller operates as expected. 144475

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by: John A05/26/2016

Small easy to install item. I used the adapter cable to connect to my pre wired motor home and it could not have been easier. Operating instructions share simp,e to follow. 251913

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by: John A05/26/2016

Small easy to install item. I used the adapter cable to connect to my pre wired motor home and it could not have been easier. Operating instructions share simp,e to follow. 251912

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by: Fabio W08/07/2013

Order it on Friday got it on Wednesday ! Fast service. Installed it in 5 minutes while cooking on the grill. Works very good for price! Will buy again when I get a new truck 93826

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by: Tim04/10/2016

I installed my new Curtis electric brake controller, connection cable, and 7 blade plug. Everything works great. Seamless installation with easy to follow instructions. 243684

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by: jerry l04/04/2017

Brake control was shipped very fast but the mounting screws were missing. Contacted etrailer and they shipped them asap. Very good to deal with, will buy from again. 364528

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by: Bill C04/10/2014

Everything was easy to install thanks to the Etrailer video on Youtube. I got it all done in about 20 minutes and it all works great. I highly recommend this company. 124478

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by: Gary W.12/16/2014

Controller works great. Also, good support from e-trailer. I emailed in on a question about wire size and got a fast answer. Product and e-trailer ROCKS for me !! 165648

Show More Reviews

Ask the Experts about this Curt Brake Controller
Do you have a question about this Brake Controller?

  • Brake Controller Installation on 2011 Toyota Tundra
  • If your 2011 Tundra has the factory tow package, which includes the factory installed 7-way trailer connector on the rear bumper, it will be equipped with the tow package plug under the dash, as shown in the photo I've edited for you. Some models with the factory 4-pole (or 4-pin) trailer connector will also have the plug under the dash, you'll need to look for a white plug located above and to the left of the emergency brake pedal, above the toe kick. Occasionally, the plug will be located...
    view full answer...

  • Curt Discovery Brake Controller Shows OL Error When Trailer is Connected
  • It is possible that it is a simple wiring issue that is causing the errors on your Curt Discovery brake controller # C51120. On your 2010 Chevy Silverado, there is a tow package wire bundle under the dash to wire in a brake controller. The tow package red goes to brake controller black. White goes to white, blue to blue, and the light blue or orange wire on the truck goes to the brake controller red wire. The OL indicates an overload and if all of the connections at the brake controller...
    view full answer...

  • Curt Brake Controller and Wiring Harness for a 2015 Ford F-150
  • For a Curt Discovery brake controller # C51120 you will need wiring harness # C51436 for your 2015 Ford F-150. I have linked video reviews for both parts for you.
    view full answer...

  • Troubleshooting Brake Controller that Flashes When Connected to Trailer
  • It sounds like the problem is corrosion on the trailer 7-way brake output circuit which is causing the controller to only show an intermittent connection. Try cleaning off this pin on the 7-way with some fine grit sandpaper. Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part # 3808, you should get output to the...
    view full answer...

  • Brake Controller Installation Harness Recommendation for a 2015 Chevy Suburban
  • Yes, there is a port under the dash of your 2015 Chevy Suburban that will allow for a painless installation of a brake controller that won't require splicing. The harness to go along with the Curt Brake Controller part # C51120 that you referenced is the part # C51452. If you went with our most popular brake controller, the P2 part # 90885 you would only need the harness part # 3016. See the install video I attached.
    view full answer...

  • Brake Controller Install in 2014 GMC Sierra
  • The install procedure will depend on if you have a 1500 or a 2500/3500 Series. If your Sierra is a 1500 model, you will need a brake controller wiring adapter harness, part # C51451. The 2500 and 3500 series would have the tow package wiring that sits above where the driver's left knee sits. If you click the video link I've provided, you can see a controller being installed in a 2014 GMC Sierra 1500. The FAQ link I provided shows how to install a controller in the 2500/3500 model. The...
    view full answer...

  • Troubleshooting Flashing 0.0 Error Message on Curt Discovery Brake Controller # C51120
  • The troubleshooting guide included in the instructions for the Curt Discovery Brake Controller # C51120 that you referenced does not include this particular display issue, a flashing 0.0, among the possible display messages. My technical contact at Curt has never seen this particular message displayed on a Discovery brake controller. He suggested that either the display is malfunctioning or the controller is bad. Since your brakes are not engaging when you press the pedal with the trailer...
    view full answer...

  • Installing Curt Discovery Brake Controller # C51120 on 1988 Ford F150
  • To hardwire the # C51120 Curt Brake Controller, you can either cut off the existing plug on its wiring harness or use the universal pigtail, part # C51515. The universal pigtail would provide an easy way to quickly disconnect the brake controller, should it become necessary. You would then use our Brake Controller Installation Kit, part # ETBC7. If you do not already have a functional 4-pole trailer connector you would also need to install one using part # 118316. The install kit includes...
    view full answer...

  • Troubleshooting Curt # C51120 Discovery Brake Controller Showing Flashing Decimal Point on Display
  • What you're describing sounds like it could either be an interruption in the trailer brake voltage output circuit, somewhere between the controller and the trailer brakes, or you could have a defective controller. Use a circuit tester with an incandescent bulb, like part # 40376 and use the probe to pierce the insulation of the blue output wire exiting the rear of the controller and ground the alligator clip. Apply the brake pedal. If the load provided by the tester causes the display...
    view full answer...

  • Troubleshooting Curt Discovery Brake Controller Issues on Ram 1500
  • The Curt Discovery Brake Controller # C51120 is a time-delay type that is intended to send out a pre-determined amount of braking power after you have applied the vehicle brakes. The other type that is often preferred is the proportional type that will actually sense the amount of braking force in the tow vehicle and send a proportional amount of braking power to the trailer, without a time delay. Based on the symptoms you described I think the issue could be with the wiring on the trailer....
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  • How to Find and Access the Brake Light Switch Wire on a 2015 Toyota Highlander for Brake Controller
  • If you check out the video I attached you will see how we installed a brake controller in a very similar 2014 Toyota Highlander as your 2015 model. We had to remove the lower dash panel (13:00 mark of the video), to make accessing the green wire possible. The kit used for the install in the video is the part # ETBC7.
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  • Adding a 7-Way Trailer Connector and Brake Controller to a 2004 Nissan Xterra
  • I will be happy to clear up what all you will need to add the equipment to tow the trailer and activate the electric brakes. First, if your 2004 Nissan Xterra does not already have a trailer hitch you will need to add one. A popular option is Curt trailer hitch # 13183. This is a Class III hitch with a 2 inch receiver. The hitch itself is rated for 400 pounds tongue weight and 4,000 pounds gross trailer weight but limited to the vehicle capacity if lower. I also recommend etrailer...
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  • Wiring Curt Brake Controller # C51120 in 2002 GMC Sierra 1500
  • Based on your description of the problem with your Curt Discovery # C51120 Time Delayed Brake Controller one cause could be a mis-wired plug-and-play harness. Please refer to the photo provided which shows how the vehicle side of the harness should be wired. For reference I have also linked a help article concerning brake controller installations in GMC trucks. The connector should be pinned out with the four wires as shown in the provided photo. If the red wire is connected to a different...
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  • Is There an Under-Dash Brake Controller Connection Port on the 2005 Mazda B3000 DS Pickup
  • An under-dash quick-connect brake controller port is not offered by Mazda on their smaller pickups, so your brake controller will require a hard wire installation. You will use the # ETBC7 brake controller installation kit that you referenced. A video and article on installing this kit are included for you. If your truck has a 7-way already you can instead use kit # 5506. If your truck does not already have a 4-pole flat trailer connector at the rear bumper you will also need a wiring...
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  • Curt Discovery Brake Control Flashing 0.0 Troubleshooting
  • The troubleshooting guide included in the instructions for the Curt Discovery Brake Controller # C51120 that you referenced does not include this particular display issue, a flashing 0.0, among the possible display messages. My technical contact at Curt has never seen this particular message displayed on a Discovery brake controller. He suggested that either the display is malfunctioning or the controller is bad. Since your brakes are not engaging when you press the pedal with the trailer...
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  • Parts Needed to Add 7-Way and Brake Controller to 2007 Ford F-150 with 4-Way
  • If your trailer does not have brakes all you would need is the part # 37185 as an adapter to convert the 4-way to a 7-way. If you do have trailer brakes you would need the # 3035-P, the # 37185, and a brake controller. For a brake controller I would recommend the Prodigy P2 Brake Controller part # 90885. This is our best selling brake controller because of how well it works and how easy it is to set up. Follow the 4-way trailer connector wires from the trailer connector to the...
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  • Troubleshooting Curt Discovery Trailer Brake Controller # C51120 Installed in 2002 Chevrolet Tahoe
  • Thank you for your recent purchases from etrailer. I would like to suggest some additional testing before you return the Curt Discovery Trailer Brake Controller # C51120. This will help isolate the problem and confirm whether the unit is indeed defective. The code OL indicates that the controller has sensed an overload condition. Disconnect the trailer from the Tahoe. Apply your grounded tester to the pins at the 5-o-clock and 7-o-clock positions on the Tahoe 7-way, as shown on the...
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  • Issues with Brakes Not Activating with Curt Discovery Brake Controller on 2015 Ram 1500
  • I spoke with my contact at Curt about the issues you and other customers have experienced with their Curt Discovery Brake Controllers # C51120 and newer model Ram trucks. The problem stems from a low voltage output on the stoplight wire on the truck. The Discovery requires 12 volts from the stop light wire in order to recognize the signal and activate the trailer brakes. Curt has found that the newer Ram trucks often have less than 12 volts at the stop light wire when the brake pedal...
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  • Parts Needed to Install the Curt Discovery Brake Controller # C51120 on a 2013 Dodge Durango
  • The Curt Discovery Trailer Brake Controller, # C51120, and the Custom Wiring Adapter, # C51446, will work on your 2013 Dodge Durango without splicing as long as your Durango came with a factory 7-way trailer connector at the trailer hitch. The 7-way trailer connector would indicate that your truck has the factory tow package, which would include a brake controller plug under the drivers side dash. You should see a gray connector just to the left of the steering column. If your Durango...
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  • Troubleshooting Flashing Display of the Curt Discovery Brake Controller part # C51120
  • The flashing O.L. message with the Curt Discovery Brake Controller part # C51120 when there is no trailer connected indicates that there is a short somewhere on the brake output circuit. I would check all the connections you made on the blue wire from the controller and then also check the trailer connector at the rear of the vehicle looking for any exposed wire or corrosion and fix as necessary. If it only flashes O.L. when the trailer is connected the problem is the same as above but...
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  • Which Brake Pedal Stoplight Switch Does Red Brake Controller Wire Connect to on 2013 Ford Escape
  • The second generation Escape (2008-2012) used a purple and white wire for the stoplight switch, but I could find no information about your 3rd generation Escape. The best way to find the correct wire is to use a circuit tester like part # 40376 and test each of the wires. The wire that only goes hot when the brake pedal is pressed (not with the headlights or turn signals) is the wire you want to tap that red brake controller wire into.
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  • Which is Better a Time Delayed or Proportional Brake Controller
  • Between the two controller I would go with the proportional Curt Triflex part # C51140 over the time delayed Curt Discovery part # C51120. A time delay controller is so named because there is a delay between the time that you initially apply the brakes in your tow vehicle and the time that the controller reaches maximum power output. Unlike a proportional brake controller, which activates your trailer's brakes based on the deceleration of your tow vehicle, a time-delayed controller sends...
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  • Help! Curt Discovery Trailer Brake Controller # C51120 Only Shows Decimal When Brake is Applied
  • Since the Curt Discovery Trailer Brake Controller, # C51120, is still displaying the decimal when the trailer is connected, the controller is not sensing a connection with the trailer brakes. In this case the issue is most likely related to a wiring problem or brake magnet problem. I would start by making sure that there isn't any corrosion in either connector. Next, I recommend using a circuit tester like the Quickee, # 3808, to make sure that you have power on the brake controller output...
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  • Wiring Adapter for Installing Curt # C51120 Discovery Brake Controller on 2014 Ford Explorer
  • To install the Curt Discovery # C51120 brake controller on your 2014 Explorer, you'll need the Curt wiring adapter, part # C51322. The plug for the brake controller is located under the dash, behind the handle for the hood release.
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  • Curt Discovery Trailer Brake Controller # C51120 Displays Only a Red Dot After Installation
  • If your Curt Discovery Trailer Brake Controller # C51120 displays only a red dot when you do NOT have a trailer connected then this indicates that the controller's red (input signal) wire is connected to the wrong side of the brake light switch. This red wire should connect to the COLD side of the switch that has power only when you press the brake pedal. If your Discovery displays the red dot when you DO have a trailer connected then this usually indicates a problem in the trailer brake...
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  • Troubleshooting 7-Way and Brake Controller Wiring on a 1997 Dodge Ram 2500
  • To have a brake controller function properly you will need to have a 7-way on your vehicle instead of the 4-way. Don't worry, I can help you get your Ram equipped for your RV. Thanks for sending your images, they really helped explain the situation. The simplest way to install the brake controller is to hardwire the vehicle. The part you will want to do this is the # ETBC7, this will adapt your 4-way harness that you currently have and provide you with the added wiring to make the...
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  • Brake Controller Wiring Harness for Curt Discovery in 2017 Chevrolet Colorado
  • Brake controllers are not vehicle specific technically so the Curt Discovery # C51120 will work in your 2017 Chevrolet Colorado. The reason we include them on our fit guide is because of the custom harnesses that may or may not be available. Since your truck isn't listed as of yet it's likely because Curt hasn't had a chance to test fit your truck since it's brand new and nothing has been officially confirmed. With that being said, if you have the wiring under the dash in your truck...
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Info for this part was:

Edited by:
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Expert Research:
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Expert Research:
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Written by:
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Expert Research:
Michael H

Expert Research:
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Video Edited:
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Test Fit:
Nicholas E

Expert Research:
John H

Updated by:
Adele M

Video Edited:
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Expert Research:
Adam R

Video Edited:
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Photos by:
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Test Fit:
Shane T

Expert Research:
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Test Fit:
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