I ultimately solved this with one of the EOH adapters available - it basically has a magnet so it tricks the brake controller into thinking there are electric brakes vs EOH. Works fine. I used the Deutsche Hydrapro adapter from etrailer.com but there are others from Dexter and Hydrastar as well...
Anyone had issues with EOH trailer brakes? My 2026 AT4 Ultimate towed my race trailer with electric brakes just fine 10 days ago, but I connect my boat trailer with Dexter (not Hydrastar) EOH brakes and it doesn't see the trailer brakes (although the trailer lights all work fine).
I swung by...
I don't have them either, I have an AT4 Ultimate (includes Max trailering), and they didn't show up when I connected a trailer. I don't have Enhanced Trailering Options either, but GMC doesn't list this as part of that package.
Super frustrated with this.
It's still an advantage even if you don't plug it in regularly, because it captures energy lost to braking and turns it into acceleration. And who doesn't love acceleration?
I am increasingly sure that the cards are just the first step in offering Apple CarKey via an OTA update.
https://www.macrumors.com/2025/12/15/gm-plans-to-roll-out-iphone-car-keys/
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.