Aftermarket Trailer Brake Controller -- DIY how-to install instructions

[Gastan]

I posted this in another thread and thought it'd be a good resource to post in its own thread for future reference.

If your 2025 4Runner doesn't come with Tow Tech Package factory installed, then it won't have a wiring harness to connect the OEM Toyota controller to under the dash. Tacoma and 4Runner owners have found that there's no way to retrofit install the OEM brake controller. Even Toyota dealerships don't have a solution to add the OEM brake controller. That leaves aftermarket trailer brake controller as the only option.

AFTERMARKET (PHYSICAL BRAKE CONTROLLER)

I've seen Tacoma owners installing Redarc trailer brake controller though, so there's aftermarket solutions at least. I've attached a couple of great installation guides for Redarc Electric Brake Controller posted by Tacoma owners:

Aftermarket Trailer Brake Install Guide #1
https://www.4runner6g.com/forum/att...tallation-for-2025-4runner-6th-gen-docx.7117/

Aftermarket Trailer Brake Install Guide #2
https://www.4runner6g.com/forum/att...instructrions-2025-4runner-6th-gen-docx.7118/

Here's what Redarc brake controller switch looks like installed in blank dash location.

AFTERMARKET (WIRELESS BRAKE CONTROLLER)

See wireless options info : https://www.4runner6g.com/forum/threads/wireless-trailer-brake-controller-options.2522/




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[olefriend]

Excellent info and install DIY writeups thanks for putting that together. That's a shame though about the lack of a harness to connect OEM brake trail controller if you don't order the tow package.

 

[Parker516]

Seems like Toyota coulda made it much easier for owners if they just included the harness anyway even if your 4Runner didn't come with tow package. I assume this was a bean counter decision?

 

[Mrknowitall]

I have the Redarc Liberty in my Silverado. Had to buy the generic pigtail and wire it to the pigtail that came with the truck- careful- red and black are backwards.
works like a champ.

 

[kinetic262]

I installed a redarc break controller on my 5th gen 4Runner and it was a snap. It came from redarc with the wiring harness that I needed. It took me about 90 minutes from start to finish to install. Somebody with more knowhow probably could've done it in 45 minutes. Happy to have a built in unit on my new 6th gen though.

 

[tustmeimlying]

If my 4runner has the tow/haul mode selector as well as the 7pin and 4pin connectors at the trailer hitch, it safe to assume I have the tow package or is there other components I am missing to use the OEM trailer brake controller

 

[rfdj]

Please check this thread
https://www.4runner6g.com/forum/threads/trailer-brake-controller-prewiring.2385/

 

[tustmeimlying]

The conclusion from that thread seems to be "I don't know, buy a tekonsha", or am I missing something lol

 

[rfdj]

The conclusion from that thread seems to be "I don't know, buy a tekonsha", or am I missing something lol

That the plug for a brake controller is there and it works and wired correctly. All major brands that made stuff for the '24 should work with the '25. Cause it worked with mine. There was a doubt that the '25 that didnt have the tow package had the harness to connect to.

 

[Peter_Offroad]

If my 4runner has the tow/haul mode selector as well as the 7pin and 4pin connectors at the trailer hitch, it safe to assume I have the tow package or is there other components I am missing to use the OEM trailer brake controller

No. My 6Gen truck had tow/haul mode selector and 7pin/4pin connectors - but no trailer brake controller.
Technically it is not needed, if you are towing below 1000lbs - above that (at least for my 4th gen) Toyota requires a brake controller be used/installed. States also have their own legal requirements (eg 2000lbs). And I would guess insurance requires as well. I assume that Toyota is not adding a brake controller to all trucks for cost reasons for this very small light weight use case - and those who do not tow.

 

[Speefk]

Gastan:

Thanks for your post! I wanted to add how installed my Tekonsha P2 using what I learned here.

First: My ultimate goal is to mount my P2 to this circled part: 55446-35010. Since I don't have the light bar or running board switches. This will require some cutting and trimming, but I don't want to cut mine up until I have an extra.

So I've come up with a solution that works, even if it's a bit unsightly. I popped the panel off with a trim tool. Prying on the sides seems easiest..

I cut a 1.25" x 3/4" piece of wood about 6" long that would serve as a mounting for the P2bracket. It fit really snug, but it's not secure. I'd say it operational, but will move it someone with longer legs bumps it hard.

I used the Tekonsha 304100 harness and grounded it with the 10mm bolt that holds the dash to the metal support.

I then incorrectly identified a black plug near the firewall, left of the brake pedal, as the connection for the harness. (This maybe were tow tech or OEM harness connects as it had the right wires and configuration, but wrong size and gender.)

But I found the proper connector up high. Thanks to the linked posts above! The proper white connector isnoted by the orange pencil.

I tucked everything in and it works. Not the tightest or cleanest fit, but it will do the trick until a backup panel is available and I can cut out the lower switches and mount the P2 to it. The wiring should remain the same in that configuration.

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