Any other advice?
2015 Trail Premium, factory 7 pin in back, factory harness and plug for brake controller.

Wired as mentioned above with solid green wire omitted and extra wire spliced in for ground to body. Tried 2 different ground points under the dash and cleaned the trailer plug connections.

All lights work, headlights & trailer running lights, turn signals/hazards and brake lights with both brake pedal and knob over-ride.

Only problem is once I push the knob I get an ABS, multi terrain and traction light.

Hate to throw in the towel and buy a harness but supposed to leave on a trip in a few days....

*edit* I tested all connections in the harness and they are good, the ground also showed good when holding the meter on the body about a foot away from the ring and clipped to pin on the vehicle side of the harness.
I thought maybe it was because I didn't have the trailer fully hooked up to the rig, just close enough to test the harness, so I hooked the trailer up and did a test drive. Went through the calibration period and then seems to function as normal in both proportional and user-control modes. Push button applies the brakes.
And I've figured out that a 4 second hold on the knob is causing the dash lights to come on. Not sure why a momentary or 3 seconds is fine but any longer than that and the rig doesn't like it.

So again, I don’t have a trailer to test so I can’t offer any real world advice. All I can tell you is that any basic brake controller or harness appear to do the same thing as the Redarc: constant 12v power in, brake pedal signal in, trailer brake output and ground. There’s no difference I can tell in the Redarc factory harness combo vs a prodigy harness and brake controller combo.

Here’s one thing that did happen to me at work once: it was a newer highlander and we couldn’t get a wireless brake controller to work right. So we hard wired in a prodigy 2 using a universal harness basically exactly as directions say. 12v direct from battery, brake pedal 12v signal with brakes applied, trailer brake output ran directly to aftermarket 7-way and ground ran directly to battery negative. System worked fine. Until you hit the manual override switch and then all sorts of warnings came on. The prodigy would back-feed to brake light circuit to illuminate brake lights, same as the Redarc is designed to do. So functionally, the 2 brake controllers do literally the exact same thing.

What I’m thinking is on the highlander the computer saw brake lights coming on without brake pedal applied so it defied its logic. This doesn’t answer why your 4Runner flags issues since it comes wired from factory ready to go, which should indicate the computer’s logic should be present. I’m curious if there’s any issues with your trailer by chance. Otherwise, I don’t really know. Everything is set up how it’s supposed to be.

Edit: so I googled the issue and it turns out a lot of Toyota’s have the problem uou describe. Apparently the 3041-P harness I dissuaded people from acquiring may have a diode installed. Looking at e-trailer they also recommend some other gizmo same as a dodge or something that will activate trailer brake lights with manual override engaged. So, Tekonsha harness may fix dash warning lights, but will make trailer brake lights not come on with manual override. Other idea is to lightly apply brake pedal with manual override and that would tell the truck you’re commanding brakes. I don’t know of a time when you would want the trailer to do 100% of the braking anyway. Normally trailers the 4Runner can tow have like terrible 10” brakes anyway. I don’t know. But it is annoying as hell to have a factory feature by such a possible flop.

I wanted to put up some links in case folks wanted to see the options

Here’s the Tekonsha harness, allegedly a diode is hidden within the wiring. This prevents warning lights, but also prevents brake lights with manual override
Amazon.com: Tekonsha 3041P Proportional Wiring Adapter: Automotive

Here’s the other item that apparently allows trailer brake lights to illuminate with manual override. It looks like it requires an additional run of wire to battery positive. Also claims its for a dodge. But etrailer recommends it.
Amazon.com: Tekonsha 30235-P Brake Control Converter and 7-Way Adapter Kit for RAM: Automotive

Screen shot of etrailer showing the recommendation

Yeah after a few more threads about this and talking to a shop that does brake controller installs who noticed it on a lot of later model Toyotas, I agree with you too.

But I may have figured a work around to get lights and manual brake (technically required here in CA) Excuse the horrible illustration but simplified explanation:

-Diode in the vehicle harness like the store bought versions to prevent back feeding the lights thus keeping the vehicle computer happy

-jump the brake wire to the stop light wire in the trailer
-diode in the trailer wiring to prevent trailer stop lights back feeding through the 7 pin into the vehicle

1. Manual button gets pushed
2. Brakes get activated
3. 12v signal from brake wire jumped to light wire
4. Stop lights come on
5. Diode prevents vehicle lights from coming on
6. Computer stays happy
7. I stay happy

All should work assuming I get the brake light wire and head light wire correct. Or else I'm gonna be locking up the brakes everytime I turn the headlights on

Maybe another diode in the jumper to be sure lights don't activate brakes?

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Yeah I drew up a diagram in which a new wire would run from the brake controller red via a diode (after a primary brake switch feed diode) and then tap into the 7 way brake light feed (hence feeding the trailer lights) and then adding a diode to the original 7 way brake feed wiring blocking a back feed there as well. It’s stupidly irritating. Creating a triangle of diodes essentially so the trailer brake light get fed from truck normally, as well as controller specifically without the controller being able to feed back to the truck. But what else can we expect from a 300,000 mile vehicle potential? I guess we can’t win them all. About to buy a few diodes and play around.

Another thing I thought of in regards to the Redarc specifically, under “proportioning” mode (normal every day driving) pushing the manual override only allows for what they call “light” braking. So from what I gather, manual override would be a pretty minimally effective trait anyway. With a more common brake controller, it would be different, as the farther the level is pulled, the more the brakes are applied. So the entire manual override for the Redarc may not even be all that useful anyhow. If preventing sway is one’s concern, investing in an anti sway weight distribution hitch like equalizer or blue ox would eliminate that most of the time anyhow. And keeping speed low too.

I wanted to correct a thought for you. You can’t use the brake command wire that feeds the brakes for lighting because the voltage varies according to braking demand. For example: set to 5 out of 10, it only provides max of 6 volts or so to trailer brakes. Therefore using that as a feed for trailer tail lights would have them dim. The whole idea of a proportioning brake controller is to vary braking based on intertial demand since the controller has no idea how hard you’re pushing on the brakes other than using a G-force sensor. Otherwise slowing coming to a stop in the truck with light pressure would allow max trailer brakes always and lock them up.

Good to know. Back to the drawing board.

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The trailer brake light circuit in the 4Runner is a 30 amp circuit, based on fuse size. Which means the Redarc likely won’t be able to power it directly. So for the truck bypass idea to work, there’s gonna need to be a relay to be activated by the Redarc to be safe. I don’t have a schematic for a 5th gen trailer socket/tail/brake lights to verify. It’s starting to look like the $80 magic box Tekonsha makes is worth it.

I was thinking the same relay route, what about a relay triggered by the brake wire that then feeds the stop lights off the 12v power coming from the 7 pin?

So the hard part is that the trailer doesn’t have one brake light. It has 2. And they’re the same as the turn signals on seperate wires at the 7-way. Whereas the 4Runner has seperate lights for turn vs brake. Somewhere they combine in a magic box of some sort to allow the trailer lights to function correctly. So you’d have to tap into the trailer brake light feed before the 7-way where it comes from the brake light feed before that magic box.

The idea or theory is to run an adjacent line along side the OEM brake light feed that comes from the Redarc itself.

So the circuit would look like this:

Brake pedal 12v when brakes applied to >diode 1> to Redarc

Same Redarc wire, but between diode 1 and Redarc >diode 2> (facing opposite way) to relay trigger line (other side of relay trigger goes to ground, anywhere)

Relay switched side: pull 12v power from somewhere, other end (connected when triggered) to OEM 7-way brake light feed BEFORE “magic box” (wherever it is)

Add diode 3 to OEM brake light feed to prevent back feeding there as well BEFORE the tap made in the previous step.

Boy that sounds terribly confusing. I’ll draw up a picture when I have time but I don’t see a way to get around it without 3 diodes and a relay.

Edit: here’s a picture


So when you apply brakes normally it would still activate the new relay, but it’s redundant anyhow. And then when you manually override, flow is blocked on both sides from back feeding. Diode number 3 would need to be heavier I think, like 15 amps or more maybe depending on what the “magic box” does. Diode number 2 is probably unnecessary now that I’m looking at it.

When I refer to a “magic box” I’m referencing the old trailer wire adapters used in older trucks that allow the turn/brake to be combined. Again, an actual wiring diagram would help immensely...

Also, the etrailer converter box I referenced is totally meant for a dodge and is not a plug and play from what I gather. It will require cutting and splicing.


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I'll be the first to admit my electrical knowledge is limited, but wouldn't it be easier to run a split (1 wire to 2 wire) from the hot 12v from the 7pin connector to 2 brake lights, controlled by a relay triggered from the brake wire?

I'm sure you're theory would work, but for some reason I'm having a hard time visualizing how you plan to get the signal to the trailer, past the vehicle without it realizing that the trailer lights are on, thus screwing with the computer. Are you planning to run wires from the harness, bypass the under dash plug and go back into the harness under the vehicle before the 7pin connector?

Yes, correct. My idea would require an extra wire to run all the way back from brake controller to trigger the new relay. And it also isn’t great since the relay would be activated any time the brake lights are commanded on. So it would always be clicking when brakes are pressed. Which is probably annoying so hiding the relay in the back would be best under my idea. You could source the 12v from the 7-way area, absolutely. And yes you could have the relay output feed both brake light/turn signal wires. But I don’t think you can use the wire that actually feeds the trailer’s physical electric brakes because that particular wire won’t be working at 12 volts. It’s proportional to my knowledge, so even when manually applying brakes the wire may only have 6 or 8 volts to operate the brakes. This may not be enough to activate the relay. Now, it may very well be enough, I’m just not sure. And each trailer/tow vehicle is set up differently. Your trailer may require a maximum setting, resulting in closer to 12 volts to feed your relay idea and it all works fine. Someone else may only have theirs set to 50% maximum and therefore is only sending max of 6-7 volts to brake down that brake trigger wire.

The thing that I don’t know for certain is how the vehicle combines/converts the turn signal brake lights to feed the trailer. Remember: the vehicle has independent turn signal and brake lights. They come from 2 different sources and are combined somehow (maybe by a “magic box” like the old trucks were, maybe by a series of diodes or computers, I honestly don’t know). The trailer lights are the same wire to do both turn and brake. There isn’t a “trailer brake light wire”, only 2 turn signals. So it’s possible to have the relay affect other operations depending on where it goes in the chain. Like maybe pushing the brake while at a stop light would make trailer turn signals no longer flash since you over-rode the circuit by wiring directly to the turn signals. That’s why I would figure it would be best to access the brake light feed from where it naturally comes from the truck before it’s converted. So it basically mimicks OEM operation with a tandem, relay and diode controlled circuit.

There is more than one way to skin a cat. And I may very well have it wrong or less simple that’s totally possible. Whatever you do, just add fuses where applicable. The ideal scenario is to get a wiring diagram to confirm how the truck’s brake/turn signals are converted to a single output.

Went to the e-trailer.com site and they have everything you need plus a video install on a 5th gen.
Couldn't ask for anything more.
Install was pretty easy after watching step by step instructions.

I went with the
- Redarc Tow Pro Elite
- Tekonsha Custom Wiring Adapter - Toyota #3041-P
- Toyota switch insert TPSI-002

Trailer finally became available and we picked it up today! 4Runner handled it with ease.



2016 Trail Premium, with KDSS if that matters.
2021 Coleman Lantern LT 17B
Blue ox weight distribution hitch with 750 lbs bars
Redarc brake controller worked great. Have it at about 6 for the short drive home and it felt just fine. trailer is 3000 lbs and only has one axle with 10” brakes so that’s not too bad by my opinion.

I’m taking a decent trip soon on the freeway and such so we shall see how it all handles. I’m thinking some air bags are in the future to help out the rear suspension. Only dropped total of 1” but that’s with an empty trailer and truck... I made sure gas tank was full though.

Took a leap and installed the Redarc Tow Pro Elite. Redarc now has a 4Runner specific harness, so no need for the Tekonsha or factory harness. I placed the brain in the kick panel and the control knob in the lower left blank below the steering wheel. The neg ground dongle was placed behind an existing ground 10mm bolt just above the left foot kick panel.

Install took about 45min total. Some notes:

1. I used the Redarc TPSI-002 blank panel for mounting the control knob. It was a perfect snap in fit into the lower left panel blank.
2. There is no need to pull out/remove the panel to access the blank. You can reach up behind the panel from below and snap out the blank. Once out, route your cable up and thru the opening. Assemble the switch, connect the cable and fit back into place in the panel. The brains of the control knob are a tight fit thru the opening, but they will go thru.
3. The white washer used on the control panel underneath the knob has some plastic casting on the back side where the LED sits. It should fit into the hole on the Redarc blank where the led passes thru, but it doesn’t. I drilled out the tiny led hole in the Redarc blank but it still didn’t fit. A sharp razor knife removed the casting so it now sits flush. You just have to hold that washer in place as you tighten down the set screw before putting on the knob.
4. My unit never went into Active Calibration mode as evidenced by flashing blue/yellow LED. It went immediately into sleep mode, or “breathing” mode as Redarc calls it. With my trailer hooked up, it worked fine. I called eTrailer and they indicated that all was fine and that the position it found itself in was sufficient for calibration. I’m going to email Redarc to be sure.

Very pleased with the smooth install, easy wiring harness and setup.




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