2024 Brake controller Problems

[Ameaux]

I just purchased a 2025 Sierra 2500 diesel and pull a fifth wheel with a solar panel (similar to the issues below).  I get a Brake Disconnect error when I apply my brakes.

 

Has General Motors (GMC and/or Chevrolet) fixed this issue?  My dealer salesperson doesn't know anything about it and when I showed him the conversation(s) on these forums, his answer was "interesting".

[64BAwagon]

Try replacing you RV's umbilical connector with a Pollak unit. https://www.etrailer.com/Trailer-Wiring/Pollak/PK12706.html?feed=npn&gad_source=1&gclid=CjwKCAiA34S7BhAtEiwACZzv4Y0UKiLCv-hPIUWIEhoM54eQGzdeiZoEoRfBCiSBQ2_w5GPzgNvBUhoCOwQQAvD_BwE

[Oneoclock]

I've read this whole thread. Thought I understood the issue completely. 

 

My boss just upgraded from his '07 gas Silverado 2500 to a '23 Diesel Silverado 2500, and it has been pulling both of his 16' dual axle trailers fine. Until he charged up the big battery that runs the hydraulic pump on the dump trailer. That's when we noticed the "Check Trailer Wiring" message in the DIC. On and off multiple times while driving, and no trailer brakes.

 

So, I have a diode and was looking into the best place to put it, but first I simply disconnected the line on the big battery which connects the emergency breakaway switch from the brake system, and this did remove the +12 V from the 7-way trailer connector. (on the +12V pin)  Seems to me this is the outcome the diode would provide, while leaving the breakaway system intact. 

 

But, even with no current feeding back on the trailer connector +12 V pin, the truck still does not like it, and continues to read "Check Trailer Wiring". 

 

The truck has no problem with the other (non-dump) enclosed trailer by the same manufacturer. Also, his '07 has no problem with either trailer.

 

I am still not understanding this system.

Edited May 8, 2025 by Oneoclock
add more info

[Oneoclock]

I have just learned that this 16' dump trailer is also not working with a Ford pickup, which shows trailer wiring notice when connected. So, I think I'm now heading in the direction of the trailer as the cause of this problem, and not the Silverado.

[chwilliams]

Another "Trailer Brakes Disabled - Service Required" message to add to the pile. '24 LTZ at ~35k miles.

 

Dealership swapped out the module, which didn't fix it and they kept it another day. Paperwork was vague on the actual solution.

[bruceb58]

27 minutes ago, chwilliams said:

Another "Trailer Brakes Disabled - Service Required" message to add to the pile. '24 LTZ at ~35k miles.

 

Do you have lithium batteries and/or a solar system in the trailer?

[chwilliams]

Nope, only tow basic stuff. I don't know if there's ever even been an LED hooked to it.

[lineman1234]

Last year i got a new to me 5ver in the early spring, no solar or lithium. Towed it 70 miles and plugged it in at my summer camp spot. That was the first tow with my new 2024 3500 gasser, and no warnings of any type. 

         I took a trip a couple months later and got the check trailer connection in about 200 feet, i checked and all was fine. I later checked and replaced the camper 7 way plug, and next trip same thing on the intermittent warning of check trailer wiring. 

        I hadnt gotten any recall yet, did a bunch of reading about it and installed a one way diode in the camper pin box, and problem solved. 

 

I recently got 3 recalls done and one being the brake part. I also just got a truck camper that came with factory 100 amp hour lithium battery and 2 100 watt solar panels. I didnt plug in the 7 way on getting it home, but will be on trips when taking them with it. So ill see if it gives any warnings with the recall done and it being solar and lithium as well as not an actual trailer with brake lights or tail lights, just marker lights. 

      Ill probably install a one way diode in the tc wiring to not need to unplug on overnight stops wandering around all winter. 

[mjonesjr84]

On 11/9/2024 at 12:02 AM, Chadw90 said:

Same here. Installed the diode on my big enclosed trailer, works great. But have the issue on my small trailer. I can install a diode here too but this isnt the solution. I often pull different trailers for work. I cant be installing diodes in every trailer. After a couple months of observing, my trailer brakes work as expected for the first little bit. It is until the trailer battery gets fully charged from the truck that it is causing an issue backfeeding to the truck. Can go from having aggressive lock up braking at gain 6 to just a slight hardly noticeable drag on gain 10. 
im thinking about an extension cable and dissecting it and installing a diode in it. Then my diode would be in the cable that i can use on every trailer. 
Ultimately there needs to be a diode on the truck side. 

Where did you install the diode, the 12v+ or the brake control wire? 

 

On 11/9/2024 at 1:38 PM, bruceb58 said:

A diode drop is typically 0.7V. You severely reduce the battery charge to the trailer by doing this if that is your goal to charge the batteries. DC to DC converter in your trailer solves the issue but you really need to bypass the 7 pin when using one. I have 3 trailers. 2 of which have DC to DC converters and one is a boat trailer that only has an EOH brake system(no charging). I have NONE of these issues that people have. Maybe it's because my GMC Denali was manufactured early 2024!

My problem with a DC to DC charger is how my RV has the 12v+ wired. It is wired to the battery side of an auto resetting breaker with the load side going straight to the 12v refrigerator. The wire powers the refrigerator very well.

 

I just drove back from NE OH to S IN today with the battery disconnected from all power in the RV and still got the disconnect message. I have checked all wiring and brakes and there are no problems. My RV is a 2023 with very little miles. I have no solar and a LiFePO4 battery. It did it even when I had the lead acid battery. It doesn't have this issue when I hook it to a different truck manufacturer. 

[bruceb58]

6 hours ago, mjonesjr84 said:

Where did you install the diode, the 12v+ or the brake control wire? 

 

My problem with a DC to DC charger is how my RV has the 12v+ wired. It is wired to the battery side of an auto resetting breaker with the load side going straight to the 12v refrigerator. The wire powers the refrigerator very well.

 

I just drove back from NE OH to S IN today with the battery disconnected from all power in the RV and still got the disconnect message. I have checked all wiring and brakes and there are no problems. My RV is a 2023 with very little miles. I have no solar and a LiFePO4 battery. It did it even when I had the lead acid battery. It doesn't have this issue when I hook it to a different truck manufacturer. 

Remove the wire on your trailer that is wired through the 7 pin connector. If you don't do that, the higher voltage is still feeding back to your truck.

 

I disconnected that wire in the junction box where the cable to the 7 pin enters.

Edited September 8, 2025 by bruceb58

[mjonesjr84]

1 hour ago, bruceb58 said:

Remove the wire on your trailer that is wired through the 7 pin connector. If you don't do that, the higher voltage is still feeding back to your truck.

 

I disconnected that wire in the junction box where the cable to the 7 pin enters.

I removed the entire battery from the equation and still had the issue. It worked fine on another truck with the battery.

[bruceb58]

On 9/7/2025 at 10:41 PM, mjonesjr84 said:

I removed the entire battery from the equation and still had the issue. It worked fine on another truck with the battery.

But do you have the DC to DC converter in there powering the trailer?

[mjonesjr84]

4 minutes ago, bruceb58 said:

But do you have the DC to DC converter in there powering the trailer?

I do not have a DC to DC converter. The LiFePO4 battery was completely unhooked but the trailer brakes would still disconnect. The emergency break away battery was still hooked up though. 

 

I talked to Hydrastar's tech support. They said in their testing with the 2024+ GM trucks, it didn't matter the type of battery. 

[bruceb58]

On 9/14/2025 at 8:16 AM, mjonesjr84 said:

I do not have a DC to DC converter. The LiFePO4 battery was completely unhooked but the trailer brakes would still disconnect. The emergency break away battery was still hooked up though. 

 

I talked to Hydrastar's tech support. They said in their testing with the 2024+ GM trucks, it didn't matter the type of battery. 

You said "My problem with a DC to DC charger is how my RV has the 12v+ wired. It is wired to the battery side of an auto resetting breaker with the load side going straight to the 12v refrigerator. The wire powers the refrigerator very well."

 

Thought that meant you had one.

 

The hydrastar likely charges the breakaway battery and the voltage ends up being higher than the vehicle voltage and must get back fed on the blue wire somehow.

 

I have two trailers with EOH controllers. One is the Titan and one is the Dexter....neither give me issues.

 

Looks like Hydrastar realizes their issue and that is why they have this:

https://hydrastarusa.com/products/2024-2025-gm-controller-adapter-module-381-7074-for-electric-over-hydraulic-system?srsltid=AfmBOopv5Agx2gCeWv-gfThXgFiqTf2WdYYIu0c3-Z4tKteGxvapVan_

 

All this is is a diode.

Edited September 18, 2025 by bruceb58

[Chadw90]

On 9/7/2025 at 3:25 PM, mjonesjr84 said:

Where did you install the diode, the 12v+ or the brake control wire? 

 

My problem with a DC to DC charger is how my RV has the 12v+ wired. It is wired to the battery side of an auto resetting breaker with the load side going straight to the 12v refrigerator. The wire powers the refrigerator very well.

 

I just drove back from NE OH to S IN today with the battery disconnected from all power in the RV and still got the disconnect message. I have checked all wiring and brakes and there are no problems. My RV is a 2023 with very little miles. I have no solar and a LiFePO4 battery. It did it even when I had the lead acid battery. It doesn't have this issue when I hook it to a different truck manufacturer. 

On the 12v wire. I bought a short extension cord, opened it up and installed a diode inline on the 12v wire