"Check Trailer Wiring" and "Trailer Brakes Connected" and intermittent loss of trailer brakes

[Boudicca908]

Last September (2025) I mentioned this issue in another thread, and said I would post a new thread when I had it resolved. The thing is -- I don't have it resolved.  I've been chasing this for months, unhappily. So I am going to share the saga, I will try to boil it down into concise bits, and maybe some of our more mechanically inclined members will have some ideas and suggestions. 

TV is a 2023 Chevy Silverado HD 2500 diesel truck.  Oliver is a 2022 Elite 2, bought new from OTT.  

In early September 2025 I needed new tires. I dropped my truck off in the late afternoon at a reputable place in Pinedale WY. I asked them to check the spare while they were working on it. The following morning they called to inform me that my batteries were dead, so I needed new batteries as well. The next afternoon I picked up my truck; by the time I arrived back at camp, it was getting dark. I shut off the truck and discovered they had turned on my overhead lights and left them on (hence my dead batteries?)... In the morning I hooked up to tow to my next destination, and began getting alternating warning messages on my dashboard and center console: "Check Trailer Wiring" and "Trailer Brakes Connected" 

I pulled over (not 5 miles from camp) and checked my 7 pin connector; it looked clean, was firmly attached, my trailer lights all seemed to be working. But the messages continued.  I could 'dismiss' these messages from the steering wheel, but they would pop back up immediately and they interrupted my view of my map on the center console, making it difficult to follow. In Denver CO, I had 10 days with family. I was convinced that something had happened to my wiring under the truck near the spare tire (wires, modules all in proximity.)  I took my truck to two Chevy GM dealerships; neither had time for me nor would they allow me to bring the TT on site, but each ran their diagnostic and both came up with these history codes: 

B1325 Control Module Power Circuit Low Voltage, failure code 0x03;  C1114 Trailer Brake Control Solenoid Valves Control Circuit, failure code 0x00; and P0562  Voltage Low, fail code 0x00. 

I call ahead to Amarillo TX dealership, explain the situation, guy on phone says he knows exactly what is wrong. Make appt. They don't do anything on Friday except change the oil; then the electrical guy is off for the weekend. I finally get the truck the next week, with this description: "Verified concern. Connected scan tool, found DTC C114 set in chassis control module, Checked trailer 7 pin connector for signs of corrosion, none found. Removed connector x188 at trailer receptacle and inspected for worn and pushed out pins, everything OK. Placed test lamp at pic c to ground and commanded low to high percentage with scan tool. Test lamp followed command from low intensity to high intensity change in bulb. Internal malfunction in k133 trailer brake control module. Replaced trailer brake control module and cleared DTC. Test drove to verify message did not appear on dash."  (They did test drive the truck -- 18 miles worth.) $400 bill. I hooked up my Oliver to pull out, and the warnings continue. All during this time, my trailer lights and brakes seem to be working fine, but the warning messages continue.

Fast forward to February. I hooked up for a short camping trip in Florida and the messages return.  **I should note: I can't keep my OTT at home, and it's in a storage facility about 50 minutes north of my home. I'm not allowed to 'work' on it at the storage facility, and I can bring it on site to my neighborhood but only for a few days each year.**  I call OTT Service dept on May 3, to check their calendar in case I need to come up before I head west for the summer; they have openings both spring and fall. I am determined to dog this thing and to try to resolve it without having to tow 900 miles to Hohenwald before my trip west. 

I have now taken the truck to 4 dealerships. They all say, "It's the trailer."  I take my truck to an independent mechanic and he says, "It's the truck, but the modules should be under warranty, so go back to the dealer for this."  Just to be sure, I find a Mobile RV Tech, tow the OTT to my neighborhood for one night, have him do his service (everything checks out fine on OTT, all working, but he finds something loose under the truck and the messages go away. But then they came back. This is exhausting. 

May 2026 -- Issue was still there, and now my trailer brakes aren't working. That is a new symptom. I say not working, but it was really intermittent; I could test with the gain control on center console and sometimes working, sometimes not.

June 3, 2026 -- Back to dealer (45 minutes north of me), "It's the trailer."  This time they let me bring OTT in tow; but they still say, "It's the trailer."  A friend suggested another independent diesel mechanic that happens to be near the dealer.  From the dealership I towed OTT to Elite Diesel in North Fort Myers, it's 3:30pm. They make a cursory review for about an hour, and say they believe it's the truck. 

June 4th, 2026 -- At this point, I am nearing departure date, so I haul trailer home, take truck back the next morning, get a ride home. Within 30 minutes they call me, "Can you tell us why your left side truck battery ground wire isn't connected? It still has the black cap on the end that it's shipped with, the cap on end of ground cable was never removed from the cable."  (I've made 5 visits to  Chevy dealerships citing need for regular service AND this electrical issue and NONE of them noticed this?)  My new mechanic thinks this has solved the issue. I get ride back up (45 min), retrieve the truck, drive home (45 min), connect the trailer, issue still there. I tow the truck and trailer both back to independent diesel mechanic (45 min).  I have work I need to do on my Oliver, so the mechanic agrees to let me do my work there (greasing my zerks in his parking lot) while they disassemble the spare tire, remove modules, check wiring in back of truck..... Now they are thinking something must be amiss in the trailer wiring. They don't stock that cable, so I might need to order one. I call OTT Service to inquire about what model or brand Oliver uses, since I've read that they are not all alike; Mike says he can't help me, transfers me to Tech Support. 

Jerry at OTT Tech Support talks to me about the 7 pin cable. He says the 7 pin cables are really the same (but Chevy Service Manual warns to use the "right one" to correctly operate the Chevy.)  Jerry gives me some solid advice -- don't let them cut the head off the 7 pin connector; if head needs replacing, take it back to the junction box under the vanity, and other tips.  I have no idea about this junction box; I can't find it in my manual or wiring diagrams, but I'm not a mechanic or electrical engineer.  Jerry sends me a series of photos that show the route of the 7 pin cable in the trailer to a junction box inside the vanity cabinet. (see below)  He says "if it has to go farther back from there, it's a really big job."  (Oh boy.) 

        

        

    

My mechanic removed the vanity panel -- immediately saw two wire connections are loose though still have the nuts on the connection (below).  ** I need to find the correct caulk (and thanks again to Jerry for providing the name of it) Silicone: ASI 335 Advanced Adhesion 100% Neutral Cure RTV Silicone, WHITE.  Until that is fixed, I won't be using my shower, since it's open to this electrical junction box.**

He tightened that down. Then he tried to find the rest of the wire, crawls under the trailer, sees wiring going into the street-side front axle where the insulation has been rubbed off. I am dumbfounded, so I wriggle under there, stick my head around the corner; these are really small wires, going through a hole in metal without any protection; they rub on that hole in the metal axle, and I see there is no grommet on the hole. This doesn't seem right to me. 

 

He wrapped it with electrician's tape. I drove around, and the issue had cleared up. I drove around some more. No warning messages. I had not crawled all the way under my Oliver before, though I have been greasing my zerks regularly; I grease the zerks from the side, not from below. I gave my phone to the mechanic and he snapped a couple of photos that I shared with Jerry, before he put the tape on. I was ecstatic, and so happy that with 3 distinct wiring issues this mechanic was willing to dog it, find them and deal with them. 

And THANK YOU JERRY.  This is June 4th. My reservations are all in place and I depart early on June 8th. 

Yesterday June 10th, I called OTT Service again to inquire about whether there should be a grommet on that hole, and if so what size or could they ship them to me? Mike says he doesn't know if there should be a grommet, doesn't know the size and doesn't sell parts; transfers me straight to Tech Support.  I talk to Jerry -- my hero -- and I send Jerry the photo from my mechanic before it had electrical tape on it.  I had already purchased some Liquid Tape, extra electrician's tape and a box of Wire Conduit (that black plastic sleeve that is used all over the OTT).  At that point in time, I was not getting the warning messages any more, but I was not entirely convinced that the tape on the wires would hold up to thousands of miles of travel.  Jerry encouraged me to keep my eye on things, and I could get it repaired during my scheduled service in October on my way to the rally before I go back home to sw Florida.  Don't you know it, less than an hour later, the messages came back. My trailer brakes seem to be working, as well as my lights, but it's very disconcerting. 

I found a Walmart parking lot and spent about an hour crawling around under my OTT. I applied more tape, put on a piece of wire conduit (sleeve) and inspected the other 3 axles. (below - you can see OLD piece of sleeve on far right side, and my new piece of sleeve, and you can see Mechanic's tape and my additional tape which is shiny and not dusty.) 

   

Additional tape and new conduit sleeve (above) on the street-side front that the Mechanic repaired. 

Other axels -- I added tape to one, shoved the grommet back into the hole on another (below). 

 

 

PHOTOGRAPHS & CREDITS:   Wiring into axle (2 photos by Elite Diesel in North Ft Myers);  Routing of 7 pin cable (5 photos by Jerry OTT Tech Support); the rest are my own photos, including my junction box with loose connections and my wire at axle with question about missing grommet (2 photos I sent to OTT); and then my 'discovery' of the grommets on the other 3 axles yesterday. 

The warning messages continue though they are sporadic.  SO FAR the brakes are working (tested by using the gain control on my center console, when traveling slow speed). 

I'm inclined to keep going on my travels. I have an appointment with OTT Service in October. 

But I am interested in any additional input, and -- if for no other purpose -- I submit this for others who might have to figure out where that 7 pin cable goes and possible places to look. *I did try to search for other threads about this, but found none. I feel certain I've seen some comments about "usually trailer ground wire issue" but didn't find it. 

Thanks to all who have been in touch, and especially JERRY at OTT Tech Support for his kind and timely service. 

*** Please note: my wifi connection is via starlink and might be sporadic, and only when I'm not traveling. ***

 

Edited 3 hours ago by Boudicca908
fixed dates