Trailer wiring question

RickR · October 2015

I need some help with what might be causing a strange error I am getting with the towing package and integrated brake controller on a 2015 Ford Expedition.

The truck is new, and we really like it for hauling stuff (like dogs). An excellent vehicle so far and we are enjoying it. It has a tow package which includes an integrated electric brake controller. There is a nifty message panel on the dashboard that allows us to set up custom settings for different trailers, go through a towing checklist, and monitor the trailer while towing. The "monitor" feature is really just the ability to see the strength of the brake controls when braking.

When we first connect the trailer, we get a "Trailer Connected" status message on the info panel. Cool. Good news. However, as we start to drive we get an alert "ding" and the message changes to "Trailer Disconnected". That's scary.

Actually, the trailer is still connected and the brakes still seem to be working fine.

As soon as we slow to a stop, the message "Trailer Connected" will pop back up and show us the status of the power to the electric brakes. Start driving again and at somewhere between 25 and 35 mph we get the "Trailer Disconnected" message.

Maybe I should not let this bother me. After all it does appear the brakes are working fine. But, I figure it is something wrong with either the truck or the trailer and it ought to be fixed, or at least understood.

I've taken the truck to the dealership (even with the trailer attached), but got little satisfaction. They put a trailer wiring tester on the truck and insist it is working as it should and the problem is with the trailer. The trailer is a 2015 T@B SMaxx, pretty new, in great condition. They won't let me take a new truck and hook it up to the trailer for fear of some kind of damage.

I am trying to locate a trailer with electric brakes (may need to rent one) to see if the problem occurs with a different trailer.

I asked the dealership "how does the truck detect that the trailer is disconnected?", thinking that would help in the troubleshooting. They say it is a loss of signal on the brake control wire (a blue wire, apparently). To me, that seems strange because, as I said, the brakes do seem to work fine even when the truck thinks the trailer is "disconnected".

With the wealth and diversity of knowledge in this community, I'm hoping someone can help with a few questions:

1. Does anyone know what triggers a "Trailer Disconnected" message on a 2015 Ford (probably an Expedition or F150, because I think they use the same system)
2. What could happen on the trailer that would change anything when driving at 25-35 mph as opposed to being stopped? Is there any change of a wire being pushed, pulled, or otherwise "changed" perhaps causing an open or short when being pulled as opposed to standing still?
3. Any other good ideas on how to diagnose whether this is the truck or the trailer other than trying to pull the trailer with a different truck or pull a different trailer with my truck?

One final piece of info. When we were driving the truck last May, having never connected or towed a trailer at any time up to that point, we got a message on the info panel "Trailer Wiring Error". That message has never occurred again, there was no log of it in the truck's engine controller, and it is a complete mystery. Perhaps this is completely unrelated to all the above, but points a finger toward the truck as the problem in my opinion.

Thanks,

Rick

Photomom · October 2015

A quick google search for "Ford Expedition trailer disconnected" turned up discussions on a couple of different forums. A quick scan seems to indicate a ground problem in the trailer.

Michigan_Mike · October 2015

I do not have a brake controller but when I looked around for this particular problem it seems to be widespread and has been occurring for quite some time. It sounds like it is a common occurrence and others have posted up remedies for it. What it sounds like is that the controller is extremely sensitive and it probably goes back to the vehicle/trailer grounding points and sensitivity to movement between your tow vehicle and the trailer.

Here are some things you might try:

1. Check the adjustment on your trailer tongue - try adjusting it and if you can remove any slop this may help out.
2. Clean up and rust on the trailer ball and apply some grease to the ball of the hitch as this could help out with the sensitivity issue.
3. Clean and treat both the truck plug and trailer plug connections. Put some dieletric grease on both connectors where they plug into one another.
4. Check the blades on the trailer connectors. If they are spread too far apart/sloppy they will not make a solid electrical connection.
5. Check the ground wires (vehicle battery ground, connection to vehicle frame, trailer ground, etc.) as a bad ground wire, corrosion or loose ground connections are typically the culprit in the majority of these problems and lighting related problems.

Loose connections create many of these types of issues with trailers and I have even squirted a little WD-40 or a small amount of lubricant in my trailer wiring connectors to promote a better point of contact and connection.

If you really want to fine tune and examine the wiring take the trailer wiring harness apart. The plastic body should come apart easily via a couple of screws and you can slide the plastic shroud back and the wiring will be exposed. Check for corrosion and the wiring ends can be cleaned up (corrosion does occur) with a small wire brush that you can buy at most parts stores. You could apply some dielectric grease on the ends of this wire and then tighten the connections down good.

Image: http://thumbs4.ebaystatic.com/d/l225/m/mRoZEqIR9NjmZbxBQQmdzrA.jpg

I believe that if you are diligent and aggressive with the above tips this is going to help remedy your problem as it sounds like this particular brake controller is extremely sensitive and produces the error message when traveling down the highway and over bumps, uneven terrain and rough roadway.

ChanW · October 2015

Is your Tab new or used?

Look in the wiring junction box that's against the bottom of the Tab under the A-frame. A couple of screws hold the cover on. See if all the connections are dry, clean, and tight in there.

Make sure your grounding wire is grounded well, on both the Tab and the truck.

Just a couple of suggestions (things I've seen cause random problems).

bigmatt · October 2015

Also check the wiring at the brakes themselves, the electric brakes power a magnet,It is possible you may have a bad electro magnet on one side,which would give you the disconnected message,but the good magnet on the other side would work,leading you to believe you have brakes,but in reality only one side is working,the best way to test,jack up trailer one side at a time,spin the wheel,manually apply the brakes using the brake controller.Many times the problem is simply a loose conection at the RV plug,when you plug into the tow vehicle.

Trailer wiring question

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