Wiring Question

[Retgw2]

Since I continue to get repeated "check trailer wiring" messages while towing I decided to change out the 7 way trailer cord to get away from the twist cap connections. Not sure if I found THE problem but did find a problem. The -/+ wires used for the brakes were contained in sheathing similar to romex wire. When the sheathing was split open the entire length of the brakes ground wire was sliced down its side exposing the copper wires. Even if it doesn't turn out to be the problem, I suppose it was worth finding to repair.

Anyway, the other interesting connection I found in the OEM 7 way trailer cord electrical box are two black lines coming from the trailer that terminate together in a twist connection. Just wondering if anyone has a guess as to what these wires go to since they aren't connected to anything associated to the 7way trailer plug?

Brian

[Jlawles2]

Trace those 2 lines. On my 303 I think they were on the break away switch.

[Retgw2]

Trace those 2 lines. On my 303 I think they were on the break away switch.

Thanks Joseph,

Was thinking that could be the case but figured somebody here would know the answer before I got into a tracing effort.

[TucsonJim]

I'm pretty sure those wires are like Joseph says above. On mine, they had a blue/white wire, red wire and black wire all connected with a twist connector. Here are some photos of mine before and after I rewired it. The black and blue/white wires were connected in the new box. The red wire was pulled back out and connected to a terminal block with +12V.

Jim

[hduring]

Brian, not sure where your problem lies, but I found this article a few years ago when we got the check trailer wiring message on our previous TT that may help you. https://static.nhtsa.gov/odi/tsbs/20...73714-9999.pdf
It’s titled = PIT5509F Diagnostic Tip - Check and/or Service Trailer Brake System message DTC C1114

[Retgw2]

Brian, not sure where your problem lies, but I found this article a few years ago when we got the check trailer wiring message on our previous TT that may help you. https://static.nhtsa.gov/odi/tsbs/20...73714-9999.pdf
It’s titled = PIT5509F Diagnostic Tip - Check and/or Service Trailer Brake System message DTC C1114

hduring Hsu

thanks for the information. I hadn't seen this particular article but on a different service bulletin the reference was similar to look for a grounding issue on the trailer. I'm hoping that by fixing the damaged ground wire for the brakes and putting in a new 7 way plug similar to what Jim TucsonJim posted above my error messages will be resolved. Fingers crossed anyway!

Brian

[StephenO]

hduring Hsu

thanks for the information. I hadn't seen this particular article but on a different service bulletin the reference was similar to look for a grounding issue on the trailer. I'm hoping that by fixing the damaged ground wire for the brakes and putting in a new 7 way plug similar to what Jim TucsonJim posted above my error messages will be resolved. Fingers crossed anyway!

Brian

When we were getting the 'trailer disconnected' message on our TV, the number one recommendation on what to check was grounding. This included the grounding connection from the truck to the trailer. When I opened the junction box on the trailer, I found one of the ground wires under the marrette was not making a solid connection. Can't remember which ground it was since there were so many under there . After redoing that connection, no more disconnect message! The upgraded junction box and 7 way cable is on my long-term to-do list...

Anyways, reading what you've done certainly sounds like you're headed in the right direction. Let us know how it works out for you!

[Country Campers]

Retgw2

Brian

Recently I have been getting this message , no trailer cord attached , just driving down the road. It has not happened yet while towing and is very random. I guess I need to tear apart the plug to check the wiring in the plug or replace the plug. Do you have the remote plug addition for the fifth wheel up on the bedside? Is this the plug that you found the bad wiring?

Brian

[Retgw2]

Retgw2

Brian

Recently I have been getting this message , no trailer cord attached , just driving down the road. It has not happened yet while towing and is very random. I guess I need to tear apart the plug to check the wiring in the plug or replace the plug. Do you have the remote plug addition for the fifth wheel up on the bedside? Is this the plug that you found the bad wiring?

Brian

Hi Brian,

I do have the extra bedside plug but the bad wiring is actually the trailer's brake wiring that connects into the junction box of the trailer cord. So far I have only had the messages while hooked up so I'm pretty sure my problem is on the trailer side.

Your example is the first I have heard with no trailer connection at all! If you look at the bottom of page four of the Bulletin that hduring posted it states that the "symptom" is caused after the system detects a trailer. .., and it is normal for the DIC to display " Check Trailer Wiring" when the trailer is disconnected from the truck while the ignition is in the run position. Not sure what to think of that since those statements seem to contradict each other?

Brian

[Country Campers]

Hi Brian,

I do have the extra bedside plug but the bad wiring is actually the trailer's brake wiring that connects into the junction box of the trailer cord. So far I have only had the messages while hooked up so I'm pretty sure my problem is on the trailer side.

Your example is the first I have heard with no trailer connection at all! If you look at the bottom of page four of the Bulletin that hduring posted it states that the "symptom" is caused after the system detects a trailer. .., and it is normal for the DIC to display " Check Trailer Wiring" when the trailer is disconnected from the truck while the ignition is in the run position. Not sure what to think of that since those statements seem to contradict each other?

Brian

Yes I have seen the "Check Trailer Wiring" when I unplug while the truck is running. And I agree with the contradicting statements , that is how I read it as well. I think I will need to pull apart the plugs and see what they look like. I have already upgraded the box on the RV so there should be no issues there.

Brian

[Ken48442]

Hi Brian,

i just had the same same issue with the check trailer wiring. About an hour into the first leg of out trip I kept getting the check trailer wiring notification on my dash. The lights on the trailer never went out and the only thing that seemed to be affected was the brakes. After some troubleshooting and wiggling wires I was able to isolate it to an issue with the front axel. The issue was with the brake wires that pass through the inside of the axel from me side of the trailer to the other. The wires rubbed enough to wear away the insulation and was grounding out the system on the axel. I got some new wire and rerouted the wires to the outside of the axel and have not had a problem since. Hope this helps your problem. Kind of a crappy design and seems like it will eventually fail on all trailers wired this way.

[Retgw2]

Hi Brian,

i just had the same same issue with the check trailer wiring. About an hour into the first leg of out trip I kept getting the check trailer wiring notification on my dash. The lights on the trailer never went out and the only thing that seemed to be affected was the brakes. After some troubleshooting and wiggling wires I was able to isolate it to an issue with the front axel. The issue was with the brake wires that pass through the inside of the axel from me side of the trailer to the other. The wires rubbed enough to wear away the insulation and was grounding out the system on the axel. I got some new wire and rerouted the wires to the outside of the axel and have not had a problem since. Hope this helps your problem. Kind of a crappy design and seems like it will eventually fail on all trailers wired this way.

Thanks for the information Ken. I was very hopeful that replacing the 7-way plug and repairing the damaged wires I located was going to fix my problem, but just got back last week and had two separate error messages again so the search continues. I will definitely start looking into the wires around the axles.

Brian