Yes, you can use jumper cables if you can establish a good ground. I know the bulbs are good, the message is just telling you there is no completed circuit. I was just using that as an example to explain what the message center is telling you.

Steve

 

I once had a heck of a time figuring out a trailer light problem...

One of the dual filament bulbs had burned out, and when it did so, one filament welded itself to the other filament... So the bulb looked like it was still working, but it wasn't, not really.

 

I had an intermittent "trailer disconnected" problem. Particularly when I hit a good bump in the road. The trailer is 2 years old, trucks a 2011. I traced the entire system from the 7 pin connector back to the trailer brakes. I found some questionable connections everywhere and correct them. Still had the fault.

What I found was the trailer company who installed the brakes used those scotch locks. Even though they were the weather resistant type with the die-electric grease, the connection was poor. The tangs that are supposed to pinch the wire were bent and the wire wasn't fully engaged. Scotch locks have NO business on anything thats exposed to the weather, period. They are OK in the cab of a truck or in the interior of a trailer...if you must use them at all. I suggest you don't. Solder and shrink tube is the best, shrink type butt-connectors are a second best. So the bottom line is you have something intermittent either in the truck or the trailer. That will cause the sensing system to alert you to a problem. Start chasing the wires.

Scotch Locks

 

Right, anything that can open the brake circuit will give a fault message. With the right equipment it is pretty easy to isolate the truck from the trailer, but an emulator that plugs into the truck seven pin is pricey for end users.

In a pinch, having a friend who has a trailer you can use to see whether a different trailer makes a difference can be a big help.

Steve

 

I will agree on the Scotch Locks 100% I would never use them for any reason.

How ever a good and well made crimp is much better then solder any day. The solder
wicks into the strands of the wire and causes loss of flexibility and an increase of strand
failure do to work hardening of the other strands. But when I say correctly made crimp
connections I don't mean using the auto parts store cheep tool or even the one from the
big box hardware stores. Making a good crimp takes a bit of learned skill.

 

Agreed. Belden, Packard, AMP, 3M etc... make the solderless crimps that are shrinkable and have the glue in them to seal out water. Its all I use on exterior connections. Note you need a proper crimping tool as well so you dont damage the connector by breaching the insulation.

 

Funny that you mention the correct crimper. I happen to have a set of tools
from DMC that make nice crimps even with the cheap auto parts store crimps.
Mind you they are no low cost tools at all. Also Amphoral and Astro make a
nice set for less. You can find other high end tool makers too. I just happen to
be hooked on DMC. >>> https://dmctools.com/default.html

 

Nice looking tools. Having spent a few minutes trying to figure it out on the web site, I have no idea what to order for typical crimp connectors.

 

HX4 and the dies you can do one of a few ways.
If your only doing AMP connectors you can go for the
two size one of the single size. The Y501 will do
#10 & #12 and #14~#26

For the Weatherpack connectors that we find on some
of the Ford plugs I would have to look it up as to what
tool to use.

EDIT : Delphi makes the Weatherpack connectors and
the miniature and sub-miniature connector types
can be crimped with AF8 and AFM8 with the correct
locators.

Now if you are doing the smaller pins on the harness
you will need other tools to do the Deutsch connectors.
The DMC AF8 is for working on the smaller pins that you
find in a lot of plugs. The AF8 is a 8 point indent type.

One way to get tools if you are not worried about the warrantee
is on Ebay. You can always order the GO-No-Go gauge set to check
the tool to make sure it is crimping fully or send it in to DMC.

Here is an HX4 that has some miles on it.
DMC Daniels MFG Corp HX4, M22520/5-01 Crimping Tool With Y501 Die | eBay

 

I WAS fighting the infamous “TRAILER DISCONNECTED” gremlin on my 2017 F150 FX4. Here are the steps I have completed so far: Installed a new trailer 7 pin plug – wired correctly by verifying each pin as they were put together. Disconnected the main trailer ground cleaned the trailer down to bare metal and installed a new ground bolt with a claw nut. Put new loop connectors on the three ground wires and bolted them down to the new ground bolt. Pulled all the marker and tail lights – cleaned the plugs on the wires and the lights. Disconnected each ground and clean the grounding point and the screw before reinstalling. Pull the trailer brake connectors and put new splices on the magnetic brake wires with lots of di-electric grease.

My final move to make the “TRAILER DISCONNECTED” go away was installed a dedicated 10 gauge wire ground wire from the truck frame to the new trailer ground bolt with a quick connect/disconnect near the back of the truck. I think what I accomplished was to educate the truck computer.

Test two, three and four were successful. I towed the trailer on a round trip of about 450 miles and HAVE NOT gotten the disconnect message again. So far, no more “TRAILER DISCONNECTED” warnings and I have tow the trailer without the ground wire connected. I am no longer connecting the dedicated ground and it probably could be removed.

 

Thanks Jaybey. I had checked that the trailer ground bolt was secure, but didn't replace it. I also installed a new 7 pin trailer plug, with LED lights. I towed following these mods but I still had the same problem. I'm going to try installing a new trailer ground bolt as you did, then a dedicated ground between the truck and trailer as well. I read elsewhere that the connection between the trailer wire plug and the truck receiver could be loose and some had wrapped some electrical tape around the plug to tighten the connection. I'll try that too I guess. I wouldn't think I'd have any loose wiring on the trailer lights or brakes

 

I’m getting a stubborn TBC fault code every time I start my 05 F350. I never had this code before. I have owned this truck since new. I did have issues with my car hauler tripping the message check trailer flashing when I was towing if I was driving on a rough rd. I had checked the grounds on trailer they are fine. I sent out my controller to be rebuilt by module repair pros. But I still have the TBC code. I replaced the 7 pin plug & cleaned the female side of the truck harness & put die electric grease checked it for power everything works but I still have the code. I checked fuses everything checks out. Is there a ground I can check on the truck somewhere? I’m getting frustrated with this.

 

What is the DTC number it is giving you?

 

Hi It didn’t give me a DTC Code # my scanner won’t bring it up. I guess I’ll have to take it to a shop that can read it properly.

 

Forscan and one of the ELM devices will do what you need with your smartphone or tablet.