2024 Denali - Trailer Brake/Brake Gain Not Recalled

[McIrish]

Bought my Truck specifically to pull a Toy Hauler and once hitched and wired up, i get several messages. Last year GMC replaced the brake modual, but it's doing it again; as I'm driving sometimes it's every 2 minutes, or 20 minutes but its driving me nuts. Plus, I'm going to Idaho next Monday and I'm oncerned...

 

My Toy Hauler has solar (Electric Brakes). I've heard the solar may be part of the issue?

 

Error Messages

1. Brake Gain Not Recalled, your trailers brake gain was not recalleddue to an error, adjust the brake gain

2. Check Trailer wiring

3. Trailer Brakes Connected

 

GMC is now telling me the issue is with the Trailer, not the truck, because the Hydrastar electronic brake system may not be compatible and that I can get an adapter at an RV store? Not what I want to hear after shelling out BIG BUCKS for the truck of my dreams.

 

Is anyone else having this problem, what is GMC telling you?

 

Help!

[McIrish]

Typo in the note, I have solar power for off grid and my trailer brakes are electric. 

[TheGeek]

Have you tried another trailer with e-brakes?  This will tell you if it's the truck or the trailer.

[redwngr]

 

 

No need to try another trailer. 

This is a know fault with the Hydrastar system.

 

Hydrastar knows they are not compatible with the 2024 and 2025 GM system.

Hydrastar sells a solution. 

 

It installs on the trailer so it does not affect only other trailers the truck might be used for.

 

This issue has been in several truck forums over the last couple years, so I'm surprised the RV community hasn't picked up on it.

I'm also surprised Hydrastar doesn't make sure its customers know about it.  

 

Hydrastar says it can result in disabled trailer braking!

Get it fixed before taking that trailer anywhere!  

 

Anyway, from Hydrastars website 

 

https://hydrastarusa.com/products/2024-2025-gm-controller-adapter-module-381-7074-381-7075?srsltid=AfmBOoonl_bGY9XFjDEZTTKZtm8rP9Bd9edM7FOBgizYFwmpnsyI4FAO

 

 

 

Edited June 6, 2025 by redwngr

[McIrish]

Redwinger and anyone else... I replaced the Trailer side wire harness as GM says some RV manufacturers install non OEM harnesses so I replaced it and installed the the GM 2024-2025 Adapter Module. It worked for about 4 hours and now I'm right back to the same problem.

 

Any advice would be appreciated; I have contacted my Dealer and they are trying to get help from GM.

 

Thanks -