2018 Tundra TRD Trailer not connected warning

I've got a new 2018 Tundra with the same issue, pulled the trailer with a 2016 Tundra and a 2009 with an aftermarket trialer controller, and no issues. The issue only happens on my 2018.

 

I have a head scratcher...I didn't even have a trailer connected and it threw that code!

Otherwise its been a great truck. We will probably just get the P3 and not bother with the stock IBC.

 

2018 TRD 4x4, having same issue. Dealer has gone over it, swapped the board with another one on the lot, had Toyota techs come out and hook up their test trailer simulator, and no results/change. Towing a Carson FunRunner and the brakes work fine with my Sequoia using a Tekonsha P3.
Next step is to get some inputs on what the TBC is looking for to determine if the trailer is 'disconnected' and then take that info to my local RV service so they can see how the trailer brake system checks out.
Frustrating...

 

Having the exact same issue, 2018 SR5 4x4 CrewMax, towing a 2017 trailer. I had no issues previously towing with my Tacoma with Tekonsha P3.

Dealer literally just dropped off my truck after changing out the control unit, no change. Yes, I am now having the dealer pick up and drop off my truck because it has been in now 6 times for this issue. Im giving up, going with the P3.

FYI since experiencing this issue with my brand new truck, I have towed my trailer with both my dads truck (Dodge with factory trailer brake control) and my brothers truck using a Teckonsha P3 with no issues.

Similarly, I have towed both my dads and brother's trailer with my Tundra and experience the same issue.

It is the TRUCK!! Do not let Toyota tell you different. In fact you should call and get a regional tech to look at the truck, as I did, and escalate this to the engineers at Toyota to get some kind of fix. Too late for us, but we could spare future owners the headache.

Phone number for Toyota 800.331.4331

 

2018 checking in (first post)!

Just tried to take our new camper and new (500 miles) 2018 Tundra into the mountains of Colorado for the weekend. Made it 2 miles, started getting the “Trailer disconnected” message. Took it back to the camper dealer, they find nothing wrong. Took it to the Toyota dealer, they had a tech hang out with us for an hour, testing everything we could test. Finally grabbed a 2017 Tundra off the used lot, no issues. Definitely an issue with the brand new truck.

Guess we will hang out at the house this weekend, since towing is totally unsafe at this point. Add another 2018 to the list.

 

I have found a fix... bare with me here I am not an electrical engineer.

To the best of my assessment here is what is going on... The IBC sends out some electrical current and if detects a certain load it will show a trailer is connected and everything works fine. If that load is outside of what Toyota engineers have deemed tolerable and programmed into the unit it will not recognize the trailer and show disconnected. It is of my opinion the tolerances Toyota programmed into our IBC, as far as what load it needs to see to detect a trailer is attached, are too tight. The ultimate fix is to have Toyota reprogram the units and loosen up the tolerance... that is not happening anytime soon.

Since we can not rely on Toyota to fix this what we need to do is increase the load that the IBC sees to "wake up" the IBC.

To do this what I have done is wired a load resistor in parallel with the electric brakes on my trailer, thus increasing the load of my trailer that the IBC sees. I bought the resistor at the the local auto parts store for $15, you get two, only need one. It is marketed toward those who change out incandescent tail lights for LED. Which coincidentally creates the same problem electrically that we are having. They are calling it an LED Load Equalizer

Anyway it worked, I drove around town for 45min and had no issues. Did not disconnect once, trailer brakes worked perfectly.

This is what I bought...

I wired this in directly at the junction box on the trailer. One wire to trailer brake ground, usually white. The other wire to trailer brake positive, usually blue.

here is a pic...

I later attached the resistor to the frame of the trailer. Apparently the thing can get hot, although mine did not, so do not mount it to or inside the plastic junction box.


This worked for my issue, hopefully it helps others.

If you are not comfortable performing this work, or do not know this is the issue with your trailer. DO NOT DO IT! Consult your trailer dealer, pass on this info and see if they can diagnose the issue for you.

Again, this is info only to help others, I do not want anyone touching their trailer that is not confident they know what they are doing. The last thing I want to do is put anyones safety at risk.

Thanks!

 

Man, so glad I saw this thread too. Big trip with a 2018 Tundra and a tried and true trailer starting next week. I can't afford any funny business. Thanks so much to all y'all that contributed to this.

 

Keith, good test results. V = IR, so a 6 ohm resistor would draw 2 amps. V/R = I. (12/6=2).

I’m retired EE and guess that maybe a smaller resistor might work, maybe a draw of 100 ma (milliamperes) which is 0.1 amp. That would be less of a load on the alternator.

For a 100 ma, R=V/I, R= 12/ 0.1 = 120 ohms. Power (watts) = I * V = 0.1 * 12 = 1.2 Watts. So you want to be conservative on the wattage rating on the resistor, so get a 5 watt one.

Summary: try 120 ohms at 5 watts. On line for approx. $ 0.52 and up.

If you have the time or inclining, maybe play around with the load resistor, and maybe see what a lvalue would be. (I.e. go higher resistance values to draw less current, 240, 510, 1000 ohms).

I’m lucky as my trailer seems to be ok without this mod, with over 600 miles and a couple trips under my belt.

 

Interesting. I've been considering selling my Tacoma for a Tundra, partly for increased towing capacity. I hope they get this straightened out.

 

Just an update, I got it repaired by toyota last week. Turns out that toyota changed them mid year. The tech spent a lot of time with toyota Corp and got it worked out. They ordered another controller, but it didn't fix the problem. So, on advice from toyota they pulled one from one newer than my 18. It fixed the problem.

 

Interesting that they swapped. Mine is officially 34 days old with the issue (counting time it sat on lot). Goes in with the trailer tomorrow.

 

I pick mine up from the dealer today they have switched out the controller. I will keep you guys informed if there is a disconnection as I am going camping this weekend.

 

If this is true, can you forward this up to corporate. Most of the '18s are having serious issues with break controlores. I about to take a 2,000 mile trip, but am worried about it now as I am nervous about losing trailer brakes while towing an 8k trailer.

 

That's what I did. Took the camper to them. The dealership is Heyward Allen Toyota in Athens, Ga. Service bay guy I dealt with is Adam. Not sure in the techs name. I'm sure they could help out if your dealership calls them.

 

I also noticed that my tundra gave "trailer disconnected" warnings at about 30 second intervals while connected to a new trailer. Testing found that both the truck and the trailer worked normally. I found that the truck was sending 25 mv pulses on the blue trailer brake wire about 3 times per second. I suppose each pulse tests the continuity of the brake wiring. I reasoned that periodically the truck was detecting the existing brake coils as an open circuit. Therefore, I added 20 ohms of resistance (2 10 ohm, 2 watt resistors in series, the two series resistors in parallel with the brake coils) between the blue brake wire and the white ground wire. That lowers the resistance slightly (1.8 ohms) and now the truck no longer sees a periodic open. I mounted the two resistors in the plug so that if there is an actual disconnect, the truck will detect it. For those who are interested, I placed 20 ohms in parallel with the two ohm brake coils. The calculation is Rt = R1 x R2/R1 + R2 or 1.81=2x20/2+20

 

Thank you! I'll get one and swap it out, test, and update everyone.

FYI.. Before putting in the resistor I was getting 2.4 ohms at the junction box on the trailer, after putting in the resistor I am getting 1.6 ohms. Just got back from a 700 mile trip with no issues.

 

Having the same problem as everyone here on this post only difference is that I had the trailer brakes rewired and I had new magnets put in and 300-400 miles later it is back to erroring every few seconds again. Tried a different trailer with my Limited Tundra and no problems. Must be certain voltage wiring harnesses that are not compatible. Anyone want to buy a trailer?

 

Get the dealer to replace the controller.

 

The controller was replaced and I tried two other Tundras, a 17 and 18.

 

Supposedly, there was a newer version of the controller made midway during the 18 models. Mine had the older version and it was continually showing disconnected. They ordered a new one, it didn't fix it. But they took one out of a newer than my tundra and it fixed it.

 

Call that Adam guy on the right. He can tell you more about it than me. He might get you to the tech idk.

 

I can't believe Toyota did not blame you for it not working. My truck did the same except pulling my boat trailer. They blamed the boat trailer. I pulled one of there trailers and it did not happen, until i pulled the other one. They looked into it for 20 minutes and said they could not replicate the problem. I hooked up my boat trailer and first time out after they looked at it, there it is. These new Pontiac Tundras are crap and so is the warranties.

 

So is what when you about hit 50 mailboxes and fly off a cliff? Cool story bro.

 

Thank you for your suggestion!

 

For troubleshooting purposes I would use individual 12vdc bulbs like a brake light bulb. Not an LED bulb. Most of these trailer emulators have leds as the indicator. The led is not a good load to determine a short or similar malfunction. Unless the circuitry is designed to add a load.

Out of curiousity are any of you having this issue running led bulbs in your tail lights as well as the trailer?

 

Anybody having this issue on a 2018, can you look in your doorjam and check the manufacture date? Mine was built in May, and will be towing this weekend(uhaul trailer), I will let everyone know what happens.

 

Mine was September. So, an early 18.

 

Hey jason thanks for the post, I'm Nick the tech that was able to solve your problem with your tundra. Hopefully this will help assists techs with this tricky problem you had with your tundra,it was a very complex situation to figure out. Anyone else needs assistance with this issue I'll be glad to help out

 

Hey jason, i'm Nick the tech that fixed the issue with your vehicle. Any techs that need assistance on this particular issue can feel free to contact me and I'll gladly help with assistance in this issue

 

Basically came down to the trailer brake ecu. I took a new tundra off the lot and swapped out the ecu. Drove around town with the trailer and not once did the message appear. Of course ordered a new ecu and when I installed it the light came on immediately. So scratching my head I took the computer i swapped with and reinstalled it. Light gone! Called toyota and evidently there is a split production year in tundras that these trailer brake ecu's were installed that are possibly enhanced internally. But still has the same part number.