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Discussion Starter · #1 ·
I keep getting this message while pulling my brand new 16' tandem. It goes from the disconnected message to the brake gain message. Then back to the disconnected message.

The lights keep working despite what message is on the dash.

I found that there was a TSB for something similar but they intended that for people having this problem without a trailer connected.

My 4 flat connection has worked flawlessly for years.

I think it must have something to do with the wiring on the trailer itself. Most likely the brake circuit. If a break away battery is bad, what are those symptoms? How do I check?

Not familiar with trailer brakes. Any help is appreciated.

Trailer has 150 miles on it. It did not do this when I first towed it home but has done it the last two times I've towed it.

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The disconnected message goes off of the electric brake circuit and is likely an issue with the ground wire although it could be brake wiring more times than not its a ground issue, the breakaway battery should not effect it. Its hard to diagnose over the computer but I would check the plug on the truck both front and back as well as ground connections on truck and trailer.
 

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Discussion Starter · #3 ·
I checked, cleaned and greased the truck side and 7 way plug. I plan to replace the ground loop for the brake circuit. I may also install a battery charger while I'm under there.

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I do know that the 2021 - 2022 have had the issue with trailer brakes suddenly not working during a trip. Stopping /starting the truck, sometimes multiple times, will get everything working again.

After more than a year of folks fussing, Ford just released the software update on April 18th that is supposed to address the problem. So it's not always hardware. Ford has fitted their integrated brake controller with a fair amount of "sensing" going on.
 
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I checked, cleaned and greased the truck side and 7 way plug. I plan to replace the ground loop for the brake circuit. I may also install a battery charger while I'm under there.
Grease is an insulator. You have an electrical connection problem and you put grease on it?

"Di-electric" is Electrical Engineer-speak for "insulator". The dielectric constant of a material measures how many volts it will hold a specified distance apart.
 

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Discussion Starter · #6 ·
Grease is an insulator. You have an electrical connection problem and you put grease on it?

"Di-electric" is Electrical Engineer-speak for "insulator". The dielectric constant of a material measures how many volts it will hold a specified distance apart.
Interesting. All I know is that I usually apply di-electric grease to any plugs that are or can be exposed to the elements.

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Eh just make sure the contacts are clean and mate tightly.
 
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My issue (same exact symptoms) was loose contacts. I had to use a pick to bend out some of the prongs in the truck connector to get a snug fit as it was intermittent. They can get loose over time connecting and unconnecting. The lights continue to work because some of the pins are fully connected while others are not.

Also had to ensure the trailer connector cable wasn't snagging on anything and allowed to freely move. That said, it could very well be software as noted above but always start with the most basic troubleshooting steps first.
 

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Discussion Starter · #9 ·
I've bent and adjusted the prongs in the truck plug. I need to use the trailer tonight so I'll see if that made any difference.

The trailer plug is always the first thing I check when I have issues with lights or anything.

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Discussion Starter · #10 · (Edited)
Bending the prongs did not help. I don't think it has anything to do with the plug fitment.

I climbed under the trailer today and found out what a mess the wiring is. The builder used incorrect colors, gauges, etc.

They had the aux circuit running to the battery but it has no charger. The strands on the ground and black were cut down to fit into an incorrect size ring terminal. All grounds are only done using self tappers, on top of the powder coating.

I spent a good long time running new wires, ground loops, etc. I have a new 7 way plug coming so that I can be sure it isn't that. Plus, the one that is on it doesn't allow me to move the wires around so the colors match with the trailer. No more of the red to yellow, green to brown, brown to green....idiocy!

Frustrating.

They used white wire for everything...I'll get it fixed and colored correctly. If this doesn't solve things then the only thing left is a trip to the dealer for the software update.



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Discussion Starter · #11 · (Edited)
Okay so I finally went and picked up the trailer. Installed the new front 7way plug. Backed the truck up to test everything. All lights worked as they should but as soon as I hit the brake I get the trailer disconnected message.

Similar thing when I squoze the traile brake controller lever. It starts ramping up then bam, trailer disconnected.

I can hear the magnet on the driver side wheel buzzing but the wheel still turns easily. I videod the noise, maybe I'll upload to YouTube for you all to listen. Towards the end of the video you can hear it start sputtering....that's about the time the trailer disconnects.

Often times it disconnects and reconnects while driving, not using the brakes at all.

I've never had trailer brakes that weren't surge only so I do not know what normal is.

I called the trailer builder and told them I need this brand new trailer fixed. It is an hour each way and with gas prices I am not a happy person.

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Discussion Starter · #13 ·
Well this is a new development. When you manually squeeze the TBC the whole instrument cluster freaks out.

The brakes do apply though so that's good. I cannot get them to lock up when driving normally even with the gain set to its max of 10.


I'm thinking it is the truck more than the trailer at this point. Unfortunately they can't get it in until Tuesday.

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There have been some problematic TBC's on the newer builds.
 

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Discussion Starter · #15 ·
This is a 2015 but I guess that's kind of "newer". Anyone know if Motorcraft has an updated TBC part # that resolved any issues?

There was that TSB that was intended to address the trailer disconnected error but that was only software I believe.

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Oh sorry. It's the 20's and 21's I believe are having TBC issues.
 
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Discussion Starter · #17 ·
Oh sorry. It's the 20's and 21's I believe are having TBC issues.
...and my 2015. LOL

I never used the 7way plug until this year. The 4 flat always worked fine. Wish I had known prior to my warranty expiring. Still, 48k miles isn't all that many. One would think something as simple as a TBC would last longer.

Of course, my throttle body took a dump a while ago so....I guess they just don't build things like they used to.

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TBC works thru the 4 way ?
 
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