Electric brake controller disabled Highlander safety system

[Dsironi]

Tk90160 was installed in my 2019 hybrid Highlander Friday. We departed for Florida on Monday with 16’ Scamp in tow.
I tested the brakes by pressing the slide. Afterward the collision detection system was disabled, contact Toyota dealer, appeared on my panel. I continued driving to first destination. Overnight the system reset, no warnings. In Champaign IL I was adjusting the power setting to the controller to b1 and the voltage wheel to 6.0. Tested the slide once again. The same warning occurred, but in addition the cruise control could not be engaged. The first was serious, but this was more serious. 1200 miles to destination!
Toyota diagnosed it to the brake switch and relay(?) being defective. Repairman cannibalized another new Highlander to fix mine.

Installer had followed instructions. I have emailed Tekonsha. Waiting for next step and not touching the slide on the controller. 👴🏻

[Steve L.]

I suggest no boost. We don't need it. Makes initial brake application harsh. Did the Toyota come with a factory tow package or was the controller installer trying to add the wiring? I have no suggestions in that regard, I'm just gathering empirical evidence that add-on wiring is just trouble.

[Carl V]

I believe a Tekonsha on a Highlander requires a diode installed in the brake wire to prevent that (brake controller back feeding the Highlander's system).

[steve dunham]

Originally Posted by Carl V

I believe a Tekonsha on a Highlander requires a diode installed in the brake wire to prevent that (brake controller back feeding the Highlander's system).

In the same vein , is your aftermarket brake controller integrated to your vehicles computer ? When you manually apply your trailer brakes the vehicle’s computer may see it as a problem with the vehicle’s ABS or the vehicle’s traction control system which may also lock out the cruise control .
The factory brake controller in my vehicle is integrated with my vehicles computer so if there is problems with the brake controller it is displayed on the vehicle’s display screen

[Carl V]

Originally Posted by steve dunham

In the same vein , is your aftermarket brake controller integrated to your vehicles computer ?

My Highlander is an older model and my Tekonsha doesn't interfere with it, and no, even on the newer Highlander models there is no brake control integration as far as I know. There are numerous posts on Toyota's forums and the eTrailer website about Tekonsha controllers causing issues. Apparently Tekonsha is aware if the issue and recommends a diode. eTrailer sells a diode kit for this purpose.

[steve dunham]

Originally Posted by Carl V

My Highlander is an older model and my Tekonsha doesn't interfere with it, and no, even on the newer Highlander models there is no brake control integration as far as I know. There are numerous posts on Toyota's forums and the eTrailer website about Tekonsha controllers causing issues. Apparently Tekonsha is aware if the issue and recommends a diode. eTrailer sells a diode kit for this purpose.

Thank you !!

[Justus C]

Originally Posted by Carl V

My Highlander is an older model and my Tekonsha doesn't interfere with it, and no, even on the newer Highlander models there is no brake control integration as far as I know. There are numerous posts on Toyota's forums and the eTrailer website about Tekonsha controllers causing issues. Apparently Tekonsha is aware if the issue and recommends a diode. eTrailer sells a diode kit for this purpose.

This is the diode I found recommended by etrailer. It's complete overkill. Tekonsha specifies a 1A diode. You can purchase a 1A diode for less than a dollar, but you'd have to solder it into the wiring or find another solution. There's not a lot of room under the driver's side so I'd just as soon spend a little extra to get something that will crimp on.

[Justus C]

Originally Posted by Justus C

This is the diode I found recommended by etrailer. It's complete overkill. Tekonsha specifies a 1A diode. You can purchase a 1A diode for less than a dollar, but you'd have to solder it into the wiring or find another solution. There's not a lot of room under the driver's side so I'd just as soon spend a little extra to get something that will crimp on.

I wanted to pop back in just in case anyone comes across this issue. The diode I referenced is the Roadmaster Single Park Diode, item # RM-690. Tekonsha doesn't recommend that diode; eTrailer does. S&H is $2.99 to my location for economy. I have not found a better price for a pre-assembled diode that includes terminal connectors.

There is pre-assembled diode on Amazon, https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1, that is just one of those basic $1 diodes with spade terminals attached and wrapped in heat shrink. If you've got some spare spade terminals (male or female as this one is assembled with both) lying around, this might be a cheaper solution. It doesn't have the convenient IN/OUT markings, nor does it have a direction of flow indicator. I plan to use a multimeter to test resistance; failing that, because it's a simple spade terminal, if your brakes aren't working you can easily swap the connection.

I think the absolute cheapest way to get this done is to get a diode for about a buck from an electronics store (e.g. Fry's) and a couple of quick splice wire connectors like so: https://www.amazon.com/3M-Splice-Con...20654247&psc=1. Crimp one end to each end of the diode and the other ends to the appropriate wires just like the installation video shows. As a matter of fact, the kit may include adequate splice connectors to do just this already. Mine's sitting in the garage waiting for a day above freezing so I'm not sure what all is left over.

[Carl V]

Great follow up, thanks!

[Justus C]

I'm back with an installation report. I spent at least 6 hours, but to be fair about an hour of that was spent removing and replacing the plastic guard under the engine compartment so I could pull out the socket that fell down in there. Much of the rest of the extra time was due to not having a lift. I do not recommend wiggling around under an unsupported vehicle. On the off chance that a tire ruptures, you will be crushed.

Here are the extra materials I needed which did not come with the kit:
-Electrical tape
-2 x 10' of 12 AWG primary wire (about $14 at local NAPA)

Here are the tools I used:
-10mm socket
-13mm socket
-Socket wrench
-Car trim removal tool
-Cordless drill with bit set
-Assorted screw drivers
-Channel lock pliers
-Flashlight
-Wire stripper (up to 10 AWG)
-Knife
-1/4" cobalt drill bit
-Needle nose pliers

The self-tapping screws in the kit can only be installed using a socket; no phillips or hex head on them. I don't recall the exact sizes (there's one big screw that grounds the plug to the chassis, and smaller ones used to attach your 20A and 40A breakers). If you don't have a way to adapt sockets to fit your drill, you'll need one.

I followed most of the steps in the eTrailer video. They must edit out a ton of fishing around for wires and swearing. I had to deviate from the video as follows:

I started by removing the 4-pin plug from the mounting plate (already welded onto the hitch). The holes didn't quite line up, so I used a 1/4" cobalt bit to open up the holes on both the welded plate and the mount that came with the kit. That allowed me to line up enough of each hole to slip the screws through and bolt it down.

I chose not to do the extra step involved in cutting the 4-pin and directly connecting the wiring. Instead I just connected the male and female 4-pins, wrapped them in electrical tape, and zip-tied them out of the way.

I don't know why he routes the duplex cable from back to front; I think it would be easier to lower it down through the engine compartment and then run it. I made use of a long plastic guard that starts under the driver's door by snaking the cable through it. That saved me some time and effort locating tie down points.

Once you get into the engine compartment, you'll realize you don't have enough wire left to go through the passenger side grommet to the driver's side via the console. So there are three options:

1) Drill a new hole in the firewall on the driver's side and route right from the engine compartment. For several reasons I believe this is a terrible idea and didn't pursue it.

2) Install the brake controller on the passenger side, which has the downside of not having easy access to the controller.

3) Buy extra cable. I found that the cable used is called primary wire and you should be able to get it in 10' lengths at any auto parts store. There's plenty of white (ground) wire, but you'll need extra to connect the blue and black wires from the wiring harness to the battery breakers. 20' of primary wire cost me $14.

Finally, I opted to use the included wire splices instead of a butt connector to tap into the brake circuit. Accessing and opening that wire loom is a royal pain, and if I had snipped the wire I don't know if I would have ever been able to connect it again.

Finding the right wire to splice into was kind of a gamble. There are two thicker green wires and it is one of those. The included voltage tester is useless, and my non-contact voltage tester would not detect DC voltage. So I ended up kind of tapping it against the wires to bring it in and out of the DC magnetic field and induce an AC voltage. It only beeped on one wire while the brake pedal was not depressed, so I knew that was not the wire I wanted. After all was done, I had my wife step on the brake while I held multimeter probes to the appropriate blades of the plug--success! Voltage present only when the brakes were depressed.

My last modification to the procedure was to use command strips to attach the brake controller holder to the console. I am not convinced that is a great idea, as the surface is not ideal for an adhesive.

[Josh68]

Originally Posted by Carl V

My Highlander is an older model and my Tekonsha doesn't interfere with it, and no, even on the newer Highlander models there is no brake control integration as far as I know. There are numerous posts on Toyota's forums and the eTrailer website about Tekonsha controllers causing issues. Apparently Tekonsha is aware if the issue and recommends a diode. eTrailer sells a diode kit for this purpose.

Carl, I'm unclear by your posts as to whether you found you needed a diode in your installation. What year of HH do you have? Thanks

[Lynn Eberhardt]

I have a Scamp 16' and a 2017 Highlander Hybrid. The 12 Volt battery is in the rear, the brake pedal switch is somewhat complex and very awkward to get at, and I wanted all wiring to be within the car.

I ran a three wire extension cord under the trim from battery area in the rear to the driver's area where the brake controller is mounted. One wire is for 12 Volts to the controller, one is for the controller voltage back to the trailer brakes, and the third is for the brake light signal to the controller.

I went out my way to eliminate any stray voltages that the car's control system might interpret as a malfunction. I used an optically isolated relay to take the brake signal Toyota provided at the trailer adapter plug. A diode probably would have worked, but I was taking no chances. I used the same system for the trailer back up lights. Everything works as it should.

[Josh68]

Thank you, Lynn

I'm an electronics idiot, so I don't know an optically-isolated relay from my rear end, but it sounds like you're affirming that there needs to be something to keep voltage only going from the brake signal line to the trailer, and not vice-versa (feedback), and I'm thinking an appropriate diode will do the trick. Not knowing exactly what I'd need, I might get the Tekonsha harness with a built-in diode, but still looking at other options.

Also, I'm trying to confirm whether I will tee into one of the wires coming out of my Tow Ready T-One connector that provisions the 4-pin trailer harness, or some other place. Still reading posts and watching videos on similar installations, to be sure I don't mess this up.

[Carl V]

Originally Posted by Josh68

Carl, I'm unclear by your posts as to whether you found you needed a diode in your installation. What year of HH do you have? Thanks

Hi Josh

My Highlander was a 2006, not hybrid (AWD V6).
I installed the Tekonsha myself, no diode, and it worked fine. But I've read afterward that some Toyota's (including Highlanders) need a diode. I don't know the specifics as to which year models are affected, hybrid or not, etc.

I now own a more recent 2013 Highlander, non-hybrid AWD V6. The previous owner also used it to tow, and already had a brake controller installed. He removed his controller before he sold it, but all the wires where still there and it was easy for me to install mine. I have no idea if there is a diode or not. Picture of my Primus IQ installation in my '13.

[Josh68]

Thanks, Carl


Still learning, here. I'm going to contact eTrailer about wiring details, including whether I'll need to run 3 wires front-to-back to run power and ground to my controller and brake signal to my 7-pin, since hybrids have the battery in back (but also access terminals in the engine bay). At the same time, I'll ask for specifics about using a diode.


I think I'm not ready to do that mod to the coin tray. I'll have to test out controller placement, but I'd like to keep that stock, if possible.

[WDavidG]

I've had the same problem with a tekonsha and my 2017 Highlander. I assume the diode as discussed will totally solve the problem. However, the disabling of Highlander functions only occurs when the manual brake lever is activated. The functions reset when the car is restarted. Since the manual braking lever is only used for a test or emergency situation I have found this to be a minor irritant and haven't bothered to install the diode.

[Raz]

A while back we were discussing the Tekonsha Prodigy brake controller. Of the folks in the discussion I was the only one whose brake lights did not come on when the manual brake switch was engaged. A few years later when my Prodigy failed and was replaced I found out why. The controller is wired to the cold side of the brake switch at the pedal. Back in the good old days that switch completed the brake light circuit and directly powered the lights. The Prodigy II took advantage of that fact and powered the lights through that connection when the manual switch was engaged. That made that wire bidirectional. It was an input when looking for the pedal pressed and an output when the manual switch was engaged. The original Prodigy did not have this feature. A nice idea except todays vehicle wiring is multiplexed and the switch down at the pedal no longer powers the brake lights directly. Meanwhile the Prodigy is still designed to power the lights. Apparently rather than redesign the the controller to the way it used to be, Tekonsha sells you a diode. FWIW just about any diode should do the job.

[Lynn Eberhardt]

Yes, I took the signal from the wire at the T-One connector. Couldn't remember the name of it last night. A diode at that point or up front at the controller would probably solve the car's over reaction problem.

I ran the three wire cord because I needed that brake signal to go to the controller. I also needed power to the controller and a line from the controller back to the seven pin. I grounded the controller up front.

[Josh68]

WDavidG, thanks for the note. Yeah, I understand that this may be an uncommon situation, but I'd like to get this all wired the way I'd like it to be, permanently, the first time, and I think adding the diode now makes sense.


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Thanks, Lynn and Raz, for the helpful details. Unfortunately, my new P2 has no diode in the harness, but apparently they sell the same connector with one inlined in the brake signal pigtail. From what I've read, it seems like I'd also be safe with an aftermarket diode, but I wonder what the amp rating should be (I've seen 10A mentioned). It may be cheaper/easier to buy the Tekonsha part 7685.


---


Lynn, on your point about running 3-wire cord, I have a follow-up question.


The HiHy has this auxiliary jump terminal box in the engine. So if I don't want to deal with the extra expense and hassle of running wires to power the brake controller from the battery itself (all the way on the other side of the car, unlike in most cars), would it be possible (and safe) to try using those terminals to provide and battery +/- to the P2, or is that unwise?


If I did that, I'd only need a small amount of cable in the engine bay, a very short run from the battery positive to the 7-pin (both in the rear), and all I'd need to run the length of the car would be the brake controller output to the 7-pin (I could use the bulk of the existing duplex I got with my eTrailer ETBC7 kit for that).

If this is a bad idea, I'll be looking for triplex wire or trying to add an extra length of 10- or 12-gauge to the duplex I have from the kit.

Also, last question. I assume from the tutorials I've seen that it's easier, and maybe only safe (?) to run the majority of the wires under the car. But if I end up needing to use the battery itself (inside the trunk) and not the auxiliary jump terminals, I wondered about the possibility of routing wires within interior trim. It seems in this scenario I wouldn't have to touch the firewall, either. I don't know, maybe that would be harder, and if it's not safe, I will just run wires under the car and through the firewall.


Thanks for any replies

[Byron Kinnaman]

Oregon Law...... If you have brakes installed they must be operational.