GM Trucks Towing disc brake trailers

[Dive Bar Casanova]

We were intermittently loosing trailer brakes.
Terrifying.

Removing the fuse that supplies truck power to the trailers batteries seemed to cure it.

Power from the trailers solar would back-feed and corrupt the trucks trailer brake module.

We didn’t have the problem but during the first free service on the truck GM replaced the brake actuator module under recall anyway.

The recall caused the problem we thought but later learned it exasperated the problem.
Pulling the fuse seemed to cure it,, but the problem returned.

I contacted GM and they gave us $750 for reporting it.
We later learned GM put a software engineer on the issue and came up with a cure. Read that: Later learned.

A modification to certain trailer electronic brake controllers on trailers with disc brakes.
Works superb.

500 + miles into the fix we are good to go.
If anyone needs the GM bulletin info PM me and I’ll send the info to you when we get home from this trip.

The head scratcher is it’s a silent fix, no owners are being contacted.

I’m thinking, that is purely guessing, the trailers standard 200 AMP solar is fine with the recall. But rigs like ours with 600 to 1000 amp over-whelms the actuators with rogue feedback power corrupting the works.

GM concurs.

All good now.
Disc brakes on a 22.000 lb trailer are well worth the investment, as long as the mulligans stay away.

Yumpin’ Yimminy this was a stressful adventure.

We’re relaxing at river sands in Az now.

 

[madweazl]

Been a known issue for a few years now and there is actually a TSB (one for pre 2024 vehicles and one for the 2024s). It can happen with any amount of solar and is most prevalent on trailers equipped with lithium batteries. If the trailers battery voltage exceeds that of the tow vehicles, it typically happens. Easy fix is to pull the fuse on your solar and the problem will go away. The GM fix seems to work in most cases but not all; there are differences in how it reacts to Hydrastar vs Dexter hydraulic actuators.

 

[Dive Bar Casanova]

Been a known issue for a few years now and there is actually a TSB (one for pre 2024 vehicles and one for the 2024s). It can happen with any amount of solar and is most prevalent on trailers equipped with lithium batteries. If the trailers battery voltage exceeds that of the tow vehicles, it typically happens. Easy fix is to pull the fuse on your solar and the problem will go away. The GM fix seems to work in most cases but not all; there are differences in how it reacts to Hydrastar vs Dexter hydraulic actuators.

We shut off the trailers solar and batteries and the problem remained.

GM dealer blamed the trailer, RV dealer service Dept blamed the truck.

Back and fourth for 6 months.

Going into the GM forums no one had an idea+ going into our RVs forums no one did either.

Calling GMC customer service no help either until a few calls more, weeks later they got back with $750 and a thank you, no cure. No referral to a TSB.

The RV dealer disconnected the solar cells on his similar rig and that allowed his brakes to work.

I can’t imagine climbing on the roof of the RV to unplug the cells every time we move.

So we took the truck to a different dealer and the service writer was familiar with the TSB and printed out what fix the trailer needed.

I took that info to the RV dealer, they were besides themselves with several units sold to GM owners with no brakes.

Three days later part ordered, fixed and good to go.

This cure is plug and play. Simple modification to the 7 point plug connections.

Our rigs Refer is DC powered off the batteries and shutting off the system and traveling 10 hours across a hot desert won’t work for us. No propane option.

This proper fix does.
I put up my experience hoping to help anyone else getting the run-around.

 

[madweazl]

We shut off the trailers solar and batteries and the problem remained.

GM dealer blamed the trailer, RV dealer service Dept blamed the truck.

Back and fourth for 6 months.

Going into the GM forums no one had an idea+ going into our RVs forums no one did either.

Calling GMC customer service no help either until a few calls more, weeks later they got back with $750 and a thank you, no cure. No referral to a TSB.

The RV dealer disconnected the solar cells on his similar rig and that allowed his brakes to work.

I can’t imagine climbing on the roof of the RV to unplug the cells every time we move.

So we took the truck to a different dealer and the service writer was familiar with the TSB and printed out what fix the trailer needed.

I took that info to the RV dealer, they were besides themselves with several units sold to GM owners with no brakes.

Three days later part ordered, fixed and good to go.

This cure is plug and play. Simple modification to the 7 point plug connections.

Our rigs Refer is DC powered off the batteries and shutting off the system and traveling 10 hours across a hot desert won’t work for us. No propane option.

This proper fix does.
I put up my experience hoping to help anyone else getting the run-around.

I'm surprised you didn't find it on a GM or RV forum; lots of us have been bitching about it. Even after the TSB most dealers had no idea about it. They didn't have the updated part until about 6 months ago so we were pulling the fuse on the solar (ours is right off the battery). Most of the disconnects don't shut off the solar, just the battery to the coach so that rarely worked but is something RV manufactures started to change in '24. Early on some guys were installing a diode in the pigtail so it wouldn't back feed (I wasn't smart enough for that). I should have bitched more to get some cash lol.

Our early build '24 GMC (March '23 I believe) didn't have this done until about 4 months ago but our latest '24 had it from the factory (April '24 build). I'm assuming you got the tailgate opening on it's own as well? If not, look into that one. Not sure if that is GMC specific or not.

 

[Dive Bar Casanova]

I’m surprised our selling dealer didn’t know it, nor did GM customer service, nor did Grand Design.
Took going elsewhere to find the cure.

May be on some VINs that the brake module recall corrected it, some VINs may need the 7pin circuit modification.

May be what system the trailer uses and maybe the Disc brake trailers even a different cure.

All that matters is it’s fixed and it took patience and perseverance to get it fixed.
I digress.