Diode Dynamics Fourth Brake Light Module Kit 2015-2023

Diode Dynamics:
91% of 100


  • Made In The USA
  • Plug And Play Kit
  • Dual Color Red And White Bulb
  • Custom Designed For S550
MSRP $80.00
You save $0.05

Diode Dynamics Fourth Brake Light Module Kit for all 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, and 2023 Mustangs.

The factory rear end on the new S550 Mustang is a head-turner, for sure. But, if you’re looking to add a subtle yet defining touch, then look no further than this Diode Dynamics Fourth Brake Light Module Kit! Specifically designed for your 2015-2023 Mustang, this kit effectively converts your single reverse light into a custom dual color switchback bulb with fourth brake light and reverse light!

Features and Benefits:
- Dual Color Red and White Switchback Bulb
- Custom Designed Specifically for S550
- Plug-And-Play For Easy Installation
- Matches Running Lights, Brake Lights & Turns White For Reverse
- White reverse light features 369 lumens of bright white visibility
- Made in the USA

Please Note: This Fourth Brake Light Module Kit will only work on US model Mustangs it is Not compatible with Euro or Australian market vehicles.

*This kit is compatible with the Tail Light Sequencer Kit (STL15). The Fourth Brake Light Kit must be plugged in first, then the Tail Light Sequencer Kit can be plugged in for a smooth operation.
*When the Fourth Brake Light Module Kit is installed on the GT350 Mustang the 4th brake light will flash with the left turn signal but won’t flash with the right turn signal.

This Diode Dynamics Fourth Brake Light Module Kit is the perfect addition to any S550! This switchback bulb allows Mustang owners to convert this location to the fourth brake light, while still retaining the reverse/backup light. This bulb will match the running lights and when you press on the brake pedal while switching to a bright white light when the vehicle is put in reverse.

Utilizing a custom red and white switchback bulb, this kit is completely plug-and-play and made in the USA!

California Residents: Proposition 65 Warning

Installation Videos

Video Transcript

The fourth brake light module has been a popular modification for our 2015 -2016 customers ever since we installed one a while back. If you're not familiar with this module, what it does, it takes your factory low mounted reverse light and converts it into a parking light and a brake light while still retaining the LED reverse light function. It gives the car a very cool custom look. Some say very reminiscent of like a Formula 1 car. With that race inspired look, it would be right at home to put this on the new Shelby GT 350. If you're wondering if it'll work, it absolutely will. It's a little bit different to install though, so we're going to walk you through it today using this 2016 GT 350.

The 4th brake light module is pretty easy to install. It's going to fit all 2015-2016 Mustangs, including the GT 350 and the GT 350R. The difference with the Shelby is a little more involved, there's 1 or 2 additional steps. Overall the installation is pretty much the same. The bulb is going to install in the factory location. This bulb will work as an LED white backup light, but will also work as a red parking light and a bright red brake light. For this installation you're going to need a lift or a jack and jack stands, 3/8 ratchet, 13mm socket, small flat head screwdriver, and a panel removal tool.

You going to start the installation by popping the trunk and we're going to remove the cover for the inflation device. Next we're going to remove this rear panel by removing these 4 thumb screws. There's going to be 2 on each side. Okay, now this panel you're going to kind of pull it forward towards the front of the car and kind of lift up. I should mention at this point, if you do have a factory sub-woofer in your car, you are going to have to remove the sub-woofer to install this part. It's only a few bolts, it's very easy to remove. Get that out of the way I'm going to actually tilt this forward and you can see the plug.

We're going to install the module on the passenger side that has the wire coming off of it. They're both the same and they are interchangeable, but it's a lot easier to fish the wire over on the passenger side than the driver side. In our case, I should mention we already have tail light sequences installed. If you have a sequencer installed there's a specific order you want everything to go in. You want to separate down here at the harness side. The sequencer goes at the tail end and then we install the 4th brake light module. That gets plugged into the chassis harness. Now we'll fish the main wire across to the other side. Just follow the factory Ford wire and go back and zip tie it later. The same thing over here. Connect at the chassis side, make sure the sequencer goes right to the light. Plug that in.

This wire here is going to be fished down to your actual backup light and get plugged in as part of the 4th brake light module. The reason we went with the passenger side with this, there's a rubber plug in the floor of the spare tire well area that's not being used. We can remove that, punch a hole in it, and fish this wire through it. This is what we're talking about right down here. This is a normal body plug. We're going to actually remove this and then punch a hole in the middle. You'll want to punch a hole in this body plug, you can use anything you want to cut a hole in it. The little screwdriver they provide actually works fine. Push that through and give it a little tear so you've got enough room there. Fish the harness through that opening. Fish it through the cut we just made. We put the wire down through the hole in the floor. Give yourself about 18 inches to 2 feet or so of wire. Fish that down there. Reinstall the plug.

Next step, move on to the car. This is where the install is going to be unique to the Shelby. In the case of the Shelby, you have a belly panel in the back. The belly pan is going to have to be removed first so we can get up to the actual reverse light. To remove the belly pan you're going to have 6 push pin clips, 2 Christmas tree clips, and then 4 bolts. 2 bolts back here and then 2 more up front. Push pins out of the way we'll remove the 2 rear bolts. The 2 front bolts are going to be right up here underneath the exhaust hangers. Don't worry about removing these 2, because if you do remove them there are little metal hooks that hold the front in place still. Now I'll remove the Christmas tree clips from the back here. You want to make sure when you remove this, remove it flat. If you've ever driven your Shelby pretty much at all, you're going to have some rocks and gravel up in here.

You can see here's our red wire we fished out earlier. Just kind of push this off to the side for now. Now what you'll want to do is reach up in here underneath the valance, below the heat exchanger for the dish cooler, then you're going to unplug the light. What you do is you turn it, just remove the whole light assembly. You can easily do the install right here actually, but we want a little more room to show you want we're doing. If you want more room, you can just reach up and pop off this little white clip. Now we're going to disconnect the bulb from the actual plug, move the housing aside, we'll go back to this in a minute. This is the factory plug. You'll notice the wires on both ends, but the middle is empty. Take the supplied screwdriver and want to basically push up the middle here and remove the little rubber plug in the center.

If you look very closely at this harness you'll see the metal clips that are already in there. You want to match the orientation with the new one. You'll notice there's a little slot at the top, the same way these are as well. That's the way you want to stick it in the back here. What we'll do is put that up in the plates. Then use the screwdriver to kind of push it through. You'll hear it click. You'll feel it clip into place. You want to make sure that the red seal pushed firmly in. Next grab the socket and remove the factory bulb and install the new switchback. Plug it into the factory wiring, click it in place. At this point it's a good idea to test it before you put everything back together and hide all the wiring. The easy thing to do is grab your keys and hit unlock. You'll know that you got it right if you get the bright light for the brake light, and the dimmer light for the parking light, you know it's working properly.

Now we're going to put the light back up into place. Turn it to lock it in. Then we're going to hide our wires. We're going to pull the wire up to the side here and tie it up to a factory harness. With the wires hidden now we can put the belly pan, rear belly pan back up into place. We're going to install both the front bolts. Then the 6 push pins. Now you can move back to the trunk. With everything connected now we can reinstall the rear trunk panel. Sure you get it all lined up. Reinstall the thumb screws. The last step, reinstall the cover for the inflator and your installation is finished.

Here you can see the 4th brake light module will first start as a parking light. You can see it as a brake light. Then finally as a white LED reverse light. The 4th brake light module is one of those cool little modifications that most people don't know are going to think came from the factory. It adds a nice, the light really ties the back of the car together. It's great to add an additional brake light. It's going to add some more safety for you, which is never a bad thing. Overall just looks cool, plus you get a nice ultra bright LED backup light. The installation is pretty straight forward. One wire to fish, not so bad. Take you about an hour, be back on the road in no time.

Vehicle Fitment

This product will fit the following Mustang years:

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