Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed
Curt Custom Wiring Adapter for Trailer Brake Controllers - Dual Plug In

Part Numbers: C51120,C51392

Our Price: $82.37
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C51120 - 360 Degrees Curt Time Delayed Controller
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Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed
part number: 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'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

California residents: click here

Curt Custom Wiring Adapter for Trailer Brake Controllers - Dual Plug In
part number: C51392

Install your Curt electric trailer brake controller quickly and easily with this custom wiring adapter. Simply plug one end of the adapter into your brake controller and then plug the other end into the built-in port beneath your vehicle's dash.


  • Plug-in wiring adapter allows for quick, simple installation of your electric trailer brake controller
  • No cutting or splicing required
    • Custom connector end plugs into the built-in port beneath the dash of your vehicle
    • Other end plugs into the back of your electric brake controller
  • Compatible with time-delayed and proportional brake controllers from Curt
    • Brake controller must have built-in plug for adapter to connect - will not work on controllers with pigtail wiring harnesses
  • 2' Long, 12-gauge wires have protective covering to deter damage
  • Limited 1-year warranty

Installation of Curt Brake Controller Adapter

To install your Curt electric brake controller, you need to connect the wiring of the controller to your vehicle. Certain auto manufacturers offer pre-wired options, typically known as tow packages, wherein wiring is run for you from the dash to the trailer connector on the back of your vehicle. When this is done, a port is installed at your dash so that you can easily plug in a brake controller.

This adapter plugs into the port on your vehicle's built-in brake control wiring harness. The harness is located underneath the dash, to the left of the steering column, and it is taped to another harness near the emergency brake pedal.

No hardwiring is required to install this adapter. After you plug it into the factory port, you simply plug the other end of the adapter directly into your electric trailer brake controller. Because there are no wires to connect, installation is not permanent. You can unplug and remove your brake controller at any time to transfer it to another vehicle or securely stow it away.

51392 Curt Quick Plug Brake Control Adaptor Harness

California residents: click here

Customer Reviews

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

Curt Custom Wiring Adapter for Trailer Brake Controllers - Dual Plug In - C51392

Average Customer Rating:  4.8 out of 5 stars   (245 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. Install your Curt electric trailer brake controller quickly and easily with this custom wiring adapter. Simply plug one end of the adapter into your brake controller and then plug the other end into the built-in port beneath your vehicle's dash.

- C51120
by: Erik03/27/2019

This is by far the most pleasant buying experience I’ve ever had online. A wealth of information is provided for installation coupled with prompt delivery makes shopping for anything RV related a no brainer for me. etrailer is wonderful and have already started recommending this website to anyone I know. 614611

No issue yet to date. Controller worked perfectly during last year’s RV season!
Erik - 04/01/2020


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by: Paul07/05/2018

This Curt Discover controller works great. Super easy to install if you get the pigtail for your model truck. I especially like the fact that you can install the bracket under the dash on my new 2018 Silverado using factory screw under the dash. No drilling required. As always wonderful pricing and delivery from E-Trailer. 533806

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by: Chris04/28/2018

Not too thrilled with this one. Three main issues listed in increasing order of magnitude. 1. One of the segments on the display died shortly after installing. 2. The adjustment wheel is very crude and hard to dial in. 3. This one is the killer, if you start by manually applying the brakes using the slider, and then put your foot on the brake pedal, and then release the lever, the BRAKES GO FULL LOCK! That's a design flaw in the circuit. 501648

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by: Keith a11/19/2018

When i needed to replace my electric brake controller on my truck for pulling my trailers I first ordered from another dealer and when i got the unit and read the instructions there were about 3 items that i wasn't told about and sent it back ,so i kept searching for the controllers and came across e trailers , there were so many questions i had from my researching that when i called e trailers and talked with Preston he was so helpful in explaining the differances with controllers and i explained what i wanted and why he helped set me up with the right one .I then ordered the unit it was received faster than i expectided , it took me about 20 minutes to install the wiring harness and controller, I'm very happy with the customer service rep. Preston with help and time to explain and the choice i made thanks Preston and E trailers 584058

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by: Bob02/19/2019

Product worked as advertised. 2012 F150 already has the terminal. All adjustments work as they should with the trailer brakes. 606348

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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: Ty F.01/18/2018

Less than 1 yr after installing on a 2017 F250, controller quit working right. It would surge brake to some high number like 7 (10 being max) regardless of the controller setting which would lock up trailer brakes. Next time it would only allow a setting of 2.5 or 7.5... nothing else. Next time it would do something different. Called Curt who recommended unplugging it for awhile. Worked for awhile then started acting up again. They're going to send me a replacement. Tbd if replacement will be better. 468124

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by: Jphnny G/01/02/2020

mounted controller-hooked into socket under dashboard, worked like it should. Very easy to install. Solved the problem of running wiring and splicing into other wiring. 735265

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by: 08/24/2020


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by: Frank08/17/2020

Perfect fit. 863956

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by: Joseph07/15/2020

Makes the install a breeze. 843145

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by: Jeffrey07/08/2020

Exactly as described, arrived in reasonable time and price was right. Works great and simple install! Thank you! 830205

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by: Bob C06/22/2020

We purchased this for our 18 ft camper It is very good working brake system. We did have a wire fray but no fault of the system. We called the help line and they helped us diagnose it . Customer service is very good**** 819546

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by: Sam05/24/2020

Extremely easy to install! Video was 100% accurate to time and steps for install as well! I am very happy! 802709

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by: Dave05/20/2020

i was satisfied with this product. Even more satisfied with 801012

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by: Larry D05/19/2020

I bought a New 28' travel trailer last year and they would not let me take it home with out installing a trailer braking system. I looked online and found a quality product at a reasonable price. When it came I installed it myself and it has worked perfectly on all the trips I made last year. It came with complete instructions. I had to buy an adaptor wire to match my 250 Ford Diesel truck. When I picked up the trailer everything worked perfectly. 800190

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by: Jeff05/05/2020

This unit has worked well for me and is similar to other trailer brake units I have used. Fairly easy to install and integrate with truck wiring. Works as expected while hauling trucks and cars on the car trailer. I installed it right in front of my right knee on the dash and routed the wires down along the seam. Tight, but to be expected in a 2016 Canyon. 792862

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by: Hugh05/04/2020
2018 Ford Transit Connect

Installed the Curt Triflex in 2018 Honda Ridgeline RTL-E and was completely easy with the C51392 Honda specific wiring adapter that plugged into the Honda pre-wiring just above and left of the emergency foot brake as you look at the pedals. Like how the controller fits nicely in front of the shifter flat on the center console storage tray with a bit of Velcro to hold it and prevent movement in transit and matches the black interior trim well (didn't use the metal bracket that came with it). Have had great luck with Curt products (hitches, adapters, etc.) and this product is very well thought out. Too early to tell about long term use though. 793319

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by: Jorge G04/29/2020

Easy to install with the wire harness I purchased. I haven't really had a chance to see if it helps with the brakes because so far, nothing I've towed had electric brakes. Hoping to be able to find out one day. But I will already have the brake controller ready in case I do need it. 789693

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by: Mark H04/25/2020

My brake controller works great. Installation instructions made it very easy to install in my vehicle. Extremely happy. 785898

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by: Grant T04/11/2020

Arrived in a timely manner. Very easy to install and had great installation information. Very pleased. 777445

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by: David P04/02/2020

etrailer products and service are excellent! With their helpful videos and staff (plus a little help from Curt Manufacturing and our teardrop trailer manufacturer (CampInn)) I was able to install electric brakes on the trailer, and a controller in my vehicle by myself. I had never installed electric brakes before. Everything works perfectly! 774202

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by: Ronnie02/13/2020

Everything was just as described installed it with ease works great 750266

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by: Nativetrax01/09/2020

Great price, easy to install, works fl awlessly. 736833

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by: Brandon B12/29/2019

Had it for a year no problems. Easy to install and use it all the time. Thanks for a great product 734736

Show More Reviews

Ask the Experts about this Trailer Brake Controller

  • Brake Stoplamp Switch Wire Color For Brake Controller Install on 2016 Ford F150
  • You'll be looking for a purple and white wire, but if you're wanting to install a brake controller there is a plug and play option that would require no cutting or splicing. If you look at the installation video I've linked for you, you can see that the brake controller connector is located behind the dash, all you'll need is the correct wiring harness to connect the controller and the vehicle and you'll be good to go. If you're using a Curt brake controller like the # C51120, you would
    view full answer...

  • Curt Brake Controller Adapter Harness for a 2020 Jeep Grand Cherokee
  • In order to install the Curt Discovery Trailer Brake Controller part # C51120 on a 2020 Jeep Grand Cherokee you will need the Curt Custom Wiring Adapter for Trailer Brake Controllers part # C51446 which makes for a plug and play installation. I have attached an install video for you on a similar model year which should be the same if not similar in regards to the plug location. The brake controller harness for a Jeep Grand Cherokee has not changed since 2011.
    view full answer...

  • Installing a Brake Controller in a 2009 Chevy Suburban
  • The 2009 Chevy Suburban does not have a port to plug in a brake controller which is the same as the trucks of the same year. But it does have the tow package wire bundle up under the dash, to the left of the steering column, held together with a white tag. Pull the wire bundle out to wire in a brake controller. With Curt brake controller # C51120 you will also need pigtail # C51515. Then you can make the following connections: Vehicle red/black wire to controller black wire for 12
    view full answer...

  • How to Install Curt Discovery Brake Controller in 2008 Ford F-150 with 7-Way
  • The Curt Discovery brake controller part # C51120 that you referenced can easily fit your 2008 Ford F-150 with the custom install harness part # C51322. This plugs into the brake controller install port under the dash of your truck and then into the back of the controller and you're set.
    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...

  • Adapter Needed to Install the Curt Discovery # C51120 on a 2005 Ford F-150
  • To install the Curt Discovery Trailer Brake Controller # C51120 on your 2005 Ford F-150 you will need the Curt Custom Wiring Adapter # C51322. This connector will be found under the dash on your driver side. I have attached a video of this adapter being used to install the Curt Venturer # C51110 on a 2004 F-250 that you can use as a reference.
    view full answer...

  • 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...

  • How Does Brake Controller Install in 2012 Ford F-150
  • When installing the Curt Discover part # C51120 with the harness for your 2012 Ford F-150, part # C51436 all you'd have to do is plug in the controller and harness and you'd be set if you have the factory 7-way like it sounds like you do. It's really a pretty simple install. Otherwise you'd need a 4-way to 7-way adapter like part # 37185 and you'd have to run the wire from the truck's frame rail to the adapter and you'd be set. See attached picture for more info on that.
    view full answer...

  • Testing Curt Discovery Trailer Brake Controller With No Display
  • It is possible your Curt Discovery Trailer Brake Controller # C51120 is faulty, but first, just double check all your connections and specifically ensure the black and white wires are not reversed. Also take another look at your circuit breaker to make sure it is not blown, but if everything but the display is working, that would indicate a problem with the unit.
    view full answer...

  • 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.
    view full answer...

  • Brake Controller Wiring Adapter for a 2015 Toyota Tacoma with Factory 7-Way
  • No worries, the 5-wire harness will work just fine because the extra connection is for the illumination circuit and it's not needed. The Curt Discovery trailer brake controller # C51120 is a fit for your 2015 Toyota Tacoma and the direct fit pig tail adapter # C51362 you referenced is correct. You will simply plug the adapter # C51362 into your factory brake controller tow port and route the pigtail to the location of your choice so you can connect your brake controller # C51120.
    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...

  • 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
    view full answer...

  • OL Message on Curt Discovery Trailer Brake Controller
  • There could be a few different things happening with your Curt Discovery Trailer Brake Controller part # C51120. The first thing that could be happening is that you have a short on the red stop light switch wire. In order to rule this out you will need to probe the red wire going into the back of the brake controller. There should only be power on this wire with the brake pedal depressed. If there is when it is not then you know there is either a short in this wire or the stop light switch
    view full answer...

  • How to Access Vehicle Brake Light Signal for Trailer Brake Controller Installation
  • If your 2005 Toyota Sequoia has a factory-installed 7-way trailer connector you can install the Curt Discovery trailer brake controller # C51120 using only the mating wiring adapter part # C51362. If it does not then the installation will be hardwired. You can gain access to the vehicle brake light signal, which is what triggers the Discovery controller to generate output voltage for the trailer brakes, either by tapping into brake light wiring or by installing a fuse tap in the brake
    view full answer...

  • 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
    view full answer...

  • 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.
    view full answer...

  • Troubleshooting Brake Controller that Only Works with Manual Override Lever
  • This is a fairly common problem and the solution is the red wire of the brake controller. Make sure it is connected to a circuit that only sees voltage when the brakes are applied and none when released. Most likely the connection is the issue and just reconnecting the circuit will cause the controller to work again. You can also check to make sure that the third brake light fuse is in good condition under the hood of the vehicle as well.
    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...

  • 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...

Info for these parts were:

Edited by:
Leah B
Written by:
Lindsey S
Updated by:
Sarah W
Updated by:
Kristina F
Updated by:
Isabelle B

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