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Hi Guys,

We just drove from Indianapolis to Moab, Utah towing a 2,700 trailer with a 5,000 vehicle. Across the mountains of Colorado. I am reasonable certain that I am not exagerating to say the "check trailer wiring" warning displayed hundreds of times, if not over a thousand. To say I am pissed off if huge understatement. That warning ("check trailer wiring") would display and then the message "trailer connected" would generally happen immediately (sometimes after a few seconds). This could be random, or it could happen rapid fire a dozen or more times.

The truck is a 2015 3500 Duramax. We bought it new earlier this year. We made one other trip with this truck and trailer in May and had similar problems, although it was only at the end of the trip, and only a few times.

On this trip it did not start until about 3 hours into our trip. I ended up stopping after about 5 hours. I changed the ground (new wire lug and made certain there was good contact to the trailer frame). I also inspected the truck side connector attachment to the harness. On the trailer, I inspected all of the wiring that was not in trailer conduit. I also checked all of the terminations on the electrical connector. I couldn't correct the problem.

We then took it to a dealer in Columbia, Missouri. They were great about getting us in and having a diesel tech with trailer experience take a look. He couldn't find anything. He recommended the plug change on the trailer; but, he couldn't see anything wrong with the one we had. (I tried to buy the plug from the dealer; but, they didn't have one in stock.)

We continued driving. The problem would get worse and then better and then worse again during the first day.

Getting up on Saturday morning (the second day) and continuing our trip we drove for almost 3 hours with only one warning. Then over the next 2 hours there were 3 messages. And then in Denver the warnings began again... very annoying. Part way up the mountains we got off at a rest area and I changed the trailer-side connector. I couldn't find the GM recommended plug; but, I found a new aftermaket plug at O'Reilly. It made absolutely no difference. The plug had a much tighter feel to it; but, its performance didn't change.

On a couple of different occasions I pulled the brakeaway switch pin and the reinsterted it. The system would appear okay for a short time. Not really sure what difference that would make.

The trailer is two years old. I just inspected the brakes before this trip. The magnets look good and the wire connections look good. We pulled this same trailer with a 2011 HD 3500 on three long trips with no connectivity issues.

Not sure where to go with this... I will take it to a local dealer here for another opinion. I was told that there is no data logged for these warnings, so there is no way to check for a fault unless it is live.

What do I need to do to disconnect the integrated controller and install an aftermarket? I'd like to eliminate the truck side connector and the harness... just not sure how to do it.

Any thoughts would be appreciated.

Jeff
 

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Its the trailer plug. Happens to me all the time. Try taking a wire brush to it clean up the contacts a bit
 

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Jeff

What are you thinking?? You have a NEW TRUCK UNDER FULL WARRANTY!!! Take it back to the dealer and tell them to fix it. Take your trailer with you so they don't have an excuse for not being able to find the mistake when it's hooked up to YOUR TRAILER.

Sure you could do it yourself, but why do that? Get the ITBC working correctly now and you'll be glad you did.
 
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They'll tell him to fix his trailer plug or have sweet could not replicate on the ticket. It'd be a waste of time
 

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I cleaned up my plugs on both sides,and chased the wires for breaks and never found anything wrong.There are so many threads on this issue that it makes me believe the ITBC is faulty.Yes,some of you never have a problem with it,but then again you probably don't haul a trailer 400 miles a day,seven days a week.
 

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126,364 purchased 11/18/14. I get it from time to time but its the trailer plug or it would do it more consistently on all the trailers
 

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Yup as well as utility equipment. Ive only gotten the message on maybe 4-5 out probably 30 or more trailers ive pulled. I always chocked it up to wonderful electricians at forest river. Ive had 4 itbc fuses blow and now carry a bunch with me since the micro j-case can only be bought at a dealer
 

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Dont know if this will correct your issue, but it sure as damn corrected mine.

Ive been dealing with increasing issues with the check trailer wiring warning. Started out once in a blue moon and recent it damn near went continuous and drove me crazy. Thank god i work in the hospital or the dinging would have drove me nuts. I went through everything at the connector side, re-ran some wires, fixed the main trailer ground from the battery (it was through a thin piece of metal instead of the frame), removed the break away switch from the mix to make sure it wasnt causing issues and absolutely nothing fixed the issue. I decided to move to the axles themselves. Keep in mind my truck is brand new and the trailer is damn near brand new as well. First two axles on the passenger side on my toy hauler were covered in grease, over filled at the factory. Spent time cleaning them. The rear passenger side is where it got interesting. As soon as I pulled the drum off, the magnet falls to the ground. The clip that holds it on is missing/mia or never installed. The wiring wasnt snapped on by the clips to the arm either. It appeared that the wiring made it way to the brake drum and melted/twisted it around creating a short in the system. As soon as I pulled the wires apart, the truck said "trailer connected" I cut the wires, removed them from the housing and took the magnet out. I plan on going down to the trailer shop in the morning and buying a new magnet, but the 15 miles i put on the trailer since cutting the wire, I've had 0 issues. Attached is a picture of the magnet and wiring

While the trailer is still under factory warranty, and I know I could have had it covered, it cost me only time and the price of a new magnet. Plus I have the satisfaction of knowing I fixed, and it's April and almost every trailer ship is a minimum 1 month out if I'm paying for it and longer if the factory is paying for it.
 

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My 2015 road warrior toy hauler does this non stop. I have tried using the plug in the bed and the plug on the bumper. I've pumped dielectric grease into all the plugs, it's random. Once it starts, it does it non-stop while you drive. Constant dinging for 30-40 minutes while you drive makes me want to blow a gasket. Never had a trailer give me the problem except my toyhauler.


Sent from my iPhone using Tapatalk
 

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GM Check Trailer Wiring error msg and TSB

Thank you all for your ideas! Most of the "fixes" described in the forum will work, at least for a while, but the problem will not have been addressed.It certainly hasn't been addressed by GM in either of their TSBs PIT5311A & B (for the different years affected). In fact, GM has the audacity to blame the trailer-side wiring and/or the "...trailer-side connectors that do not meet the SAE specification".!!
Why hasn't anyone noticed (or mentioned) that the only trucks having this problem have the 7-way/4-way combo plug oriented with the 7-way on top? GM certainly won't mention it (see below), and you know the folks in the trenches in the Service Departments have probably been told not to say anything to the customer. You know the TSB did not arise out of thin air, but because of a large number of errors arising...with customers who have the combo plug with the 7-way on top. Read on, if you're interested:
The real problem, and the reason folks have not had the error with older trucks or Fords, etc. is because GM came up with a great idea that was poorly implemented. They figured combining a 7-way and 4-way plug would save using converter plugs (correct) and save customers having to carry converters for boats and other 4-way wired trailers. Probably a nice gesture overall.
However, they did not bother to spec that the 7-way has to be on the bottom of the 7/4 combination plug. If you walk a dealer's lot, you'll see some of the trucks have 7-way on top, others have it on bottom. The truck-side 7/4 combo plug snaps in very nicely to the bumper with its cute little spring clips (another good idea), but the plug can NOT be inverted to put the 7-way on the bottom, where it should be, and like it has been for years. The two bottom terminals in a 7-way, when it is normally oriented with the truck-side lid lifting UP. are the GROUND and TRAILER BRAKE.
Hence the problem with GM trucks that have the 7-way on top: as the trailer side plug and wire hang and wiggle (imagine that, what a surprise for the GM engineers!), one or both of the two terminal connections (GROUND &/or BRAKE) can lose contact intermittently, causing the "DING, DING, DING: CHECK TRAILER WIRING" followed shortly by "TRAILER CONNECTED" as the terminals reconnect. This is also why your "Trailer Gain" display on trucks that have that in the info cluster will "grey out" and not show any activity when the connection is loose, then light back up to the normal orange and show activity when the connection is tight.
The bumper stampings are apparently done in batches, or perhaps at different locations, resulting in some bumpers having the 7-way hole on top and others with the 7-way on the bottom. Since the plug can not be inverted and GM did not think to spec the bumper stampings correctly, they chose to place the source of the problem with the trailer-side wiring!! Drill and add your own ground wire indeed! Sloppy and lazy on GM's part. Or buy a new trailer-side connector (at your expense), because yours probably "...does not meet the SAE specification". Really??
The REAL fix would be for GM to swap out your current bumper stamping with one having the 7/4 combo plug oriented with the 7-way on the bottom. I can't imagine GM would ever voluntarily do this, unless there were enough safety-related problems &/or accidents involving lack of trailer braking. Why wouldn't GM at least provide the Pollak trailer-side connector to the customer and recommend they visit their favorite RV service center? Or perhaps reimburse the customer for the cost of the Pollak trailer-side connector?
All of the affected vehicles are $ 50,000 plus, so a gesture of customer goodwill on the part of GM to really fix this problem (instead of placing blame on the trailer side) would certainly be reasonable. Wait! What was I thinking?! If they can get customers to foot the bill by not being transparent about their engineering snafu (for at least five model years!), nobody in GM has to be accountable.
I'm going to buy the Pollak trailer-side plug and start surfing the local and regional salvage yards for a "correctly" stamped bumper.
Good luck to you all!
Gordon Flowers
Sacramento, CA
 

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I have been towing a 9,000lb travel trailer with my 2015 3500 DRW. The last 3 trips out we have been getting a random "Check trailer wiring" "service Trailer Brake System" "Trailer Connected" messages on the DIC. I have towed this trailer with my old truck and just started towing with this truck in March. We made 5 trips out to and from with no problem.
The first trip it happened on we were 2hours into the ride coming home. It popped on a few times saying "check trailer wiring" then would say "trailer connected". When the message occurred I could tell that my trailer running lights remained on still so I didn't figure the plug came out or the wire got damaged. We pulled over in a gas station and checked the plug and connections and all seemed good. We kept going on our way and the message didn't come on anymore.
The 2nd trip it happened on we didn't see the message in our 1 1/2 hr ride to our destination. On the way home about 1 hour into the trip, the warnings started again and kept coming off and on. Stopped and checked the plug and connection and all seemed good.
The 3rd trip out, 1 hour into the trip out it started again. Coincidentally I came over a bridge and we bounced quite a bit then it started coming on. Kept coming on and off until our destination. I noticed that when it said to "check trailer wiring" the trailer brakes wouldn't work coming down a big hill. I had tried to manually apply the trailer brakes through the factory brake controller on the dash and got nothing.
When we hooked up the trailer to leave and head home we immediately got the "Check Trailer Wiring" and "Service Trailer Brake System" messages as soon as we plugged in and hadn't moved. A buddy and I started looking over things. I checked the ground wire for the trailer connection and put a new clean end on it and reattached it firmly. No change.
We checked the Trailer brake fuse under the hood and nothing appeared blown. swapped it with another like fuse and still no change.
pulled out a test light and checked the function of all pins on the trucks 7 pin connection. When we tested the trailer brake controller pushing signal to the 7 pin connection it was completely grayed out on the dashboard and didn't send a signal to the 7 pin connection. I disconnected the back of the truck 7 pin connection behind the bumper. We tested that side with a test light and still nothing from the trailer brake termianl. We had to get on the road so we started on our drive. We still had brake lights on the trailer but there was no trailer brakes. We started driving down the road with the DING DING DING going off over 30 seconds.. IT SUCKED! about 40 minutes into the drive it stopped. The trailer brake output started showing when I hit the brakes, the manual brake controller was working properly. The rest of our 1 hr drive was uneventful. Plenty of bumps in the road and no more messages or DING noises. I tested the Trailer brake pin on the truck side again now that things were working. Still didn't show any voltage coming through and the DIC trailer brake display was grayed out. SO I am not sure that test proves anything. Maybe the trailer brake doesn't output anything unless another part of the 7 pin trailer side is connected too?
the terminals on both trailer and truck side 7 pin connection look pretty good. Very minor corrosion. I took some electronic terminal cleaner to them and scraped them up a bit. I applied some dielectric grease to both sides.

So looking for some guidance from the original post Jeff11, what did you determine to be the cause and solution?
Thanks in advance.
 

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You might check the wiring going to brakes on trailer, sounds like an intermittent open. There is also a relay or some other electrical components in the box under bed. Trace the wires back from plug on truck to that box and reset connectors.
 

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I have had the same issues on my 2017. After checking the wiring and finding no problems I changed out the wiring harness and plug on the trailer. Didn't fix anything, same message. To make a long story shorter I found when I plug the trailer plug in that if I use a small hammer to lightly tap the plug so that it has a good connection that I no longer get the message. In July I pulled the trailer to West Texas on a 9 hour trip and as we were pulling into the park the message came on. I don't know if if this was helpful or not, but it is easy to check.
 

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So thanks for the replies guy. I hit the original poster up on PM. He linked his problem to the true alter. I went and looked at my trailer today. I popped one tire off and got under the drum and found a broken wire running to my magnet for the emergency brake.
I have the part on order to replace but I’m pretty sure that’s going to be the problem.
I recently hit a curb pretty good in a tight gas steroid parking lot. Must have knocked the wire loose and got it stuck inside the bearing as it rotated. I’m guess it was intermittent If the wires some how made a connection and made it turn off.
 

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I bought a new oem break controller because the old one sucked going off all the time.Just drove 2500 miles with the new one.
At 700 and then at 1100 miles I got a quick check trailer,connected.Maybe 2 more times in the 2500 miles.
Way better controller than original dash puncher! That one drove me nuts. I’m talking totally missing a song on the radio!
Wish I knew of the bad part long ago.Not that it did it all the time but when it did it sucked,the old one that is.
If this one goes hay wire 1 time I’ll install a prodigy.
 

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I've got a 2018 and Haul a slide in Truck camper. Mine does this constantly plugged into the bed connector if my light selector is in the Auto mode. It stops when I move in one click to the right. it's done it since new.
 

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2016 Yukon XL

I got the same message for a few hundred miles a year ago while pulling a 30 ft RV and then it disappeared. Now it started again with no trailer connected!
 

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My 2018 3500 had the same warning. Turned out to be a loose harness going into the fender well for the in bed connector. I secured the factory harness connector which had come loose, then added a zip tie. Evidently it got rattled enough that it kept triggering the warning. On my trip from Georgia to California the warning would come up several times a day. On my trip back after my repair, it didn’t come on once. In fact it hasn’t happened at all since, and it’s been a year and several thousand miles towing. Might be a long shot but I’d check the wire loom coming from the in bed connector and see if the harness is secure.
 
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