Brake controller issues on 2024 GM HD trucks

[familytruckster4]

I ran across this document on another forum and figured I should share it. 6379278 is the document I.D. number from GM.

[Cate&Rob]

familytruckster4 Good find! Thanks for posting.

Rob

[Jlawles2]

I've been thinking about that issue with people using Li Batteries that carry a higher charge than the truck and possibly causing issues.

What comes to mind is a Diode on the power line from the truck. something like https://www.ebay.com/itm/38500640601...saAqV_EALw_wcB that when trailer voltage exceeds truck voltage, it shuts down the flow.

[Jkwilson]

How does the trailer battery voltage get to the brake controller? The only time there would be a connection between the trailer 12V system and the brake controller output is when the breakaway cable is pulled. The power side of the trailer to truck connection isn’t going to negatively affect function of the brake controller or anything else in the truck. I think it’s a red herring.

My guess is it’s fooling the GM trailer detection system which has had issues for a few years. They used to detect the trailer by pulsing voltage to the lights and looking for current, but maybe they are looking for the presence of a breakaway power source on the 12V charge line now before enabling trailer brakes. If the trailer battery is at a higher voltage than the truck electrical system, it might see no current flow from truck to trailer on the charge line and assume no trailer with brakes is attached.

[Jlawles2]

I think the entire 7 way plug on the back of the truck runs through a module. This would include the 12V power source. Once the power from the camper back feeds into the module (which is also the brake controller) it trips.

[Jlawles2]

I kept looking around and found https://www.etrailer.com/Accessories...er/RM-690.html Not a big fan of the spade connectors, but it's rated at 84 amps (way more than needed) and should prevent back feeding of the camper battery into the truck.

[familytruckster4]

Thats my understanding as well. The 2024 electrical architecture is all new. That was a big part of the changeover from the 23 models, other than the minor cosmetic changes the electronics changes are significant

I suspect theres already an update in the works for the module. Some of them can now be done on an ongoing basis over the air.

[WondersAwait]

This is great to know, thanks for posting. I am considering trading in my 22 for a 24 so I'll have to look into this a bit further and see if anyone on the GM truck boards have used a diode system to solve this like Joseph posted.

[Jkwilson]

I think the entire 7 way plug on the back of the truck runs through a module. This would include the 12V power source. Once the power from the camper back feeds into the module (which is also the brake controller) it trips.

But 12V items on a vehicle should have no issues with even 16 or 18V being applied. 14.5V would be common from the alternator.

[Jlawles2]

Jkwilson Agree to an extent, but the issue is the module sees power flowing in the wrong direction. Once the module see's inverted flow it shuts down the circuit and trips the code. True the alternator is capable of putting out 14.5VDC (on my 18 I see this on a rare occasion), circuits should be able to handle 15VDC or a bit more, but it becomes tricky because there is a limit to the variance before the voltage regulators can not regulate the voltage going to sensors and can lead to in accurate readings or even failure.

I would imagine this probably has something to do with preventing surges from the trailer supplying voltage into the truck and damaging the circuitry. Think along the lines of say a power line strike by the trailer feeding high AC current in to the systems.

[uwskier]

I have a 2024 and saw this message of brakes disconnecting. I've unplugged my solar charge controller and am about to head out on a cross country trek. I WILL be running the generator while driving to keep the trailer cool-ish, but the WFCO should mostly be in float voltage of 13.2 so I don't expect the truck, which will be pushing closer to 14, should take issue with that. Would suck to have to disable my converter. Is there a way to even do that easily yet keep 12v to the fridge working?

[Jlawles2]

uwskier You could follow the 12V power line from the whip cord to the junction point and disconnect it there. With solar and a generator you do not need the constant power supply to charge the house battery for the brake away switch.

Ideally putting a switch in the line would be better if possible as this keeps the possibility of suppling power to the unit if needed from the TV.

[JRKJR]

I've been thinking about that issue with people using Li Batteries that carry a higher charge than the truck and possibly causing issues.

I don't have solar but I do run lithium's. Only had 2 short pulls with the new truck so far but I have not had any issue's (knock on wood)

[Mark56]

I've got a 2024 Chevy HD hooked to a 2023 303RLS. First tow (500 miles) brought a LOT of trailer brake warnings and disconnections. Put a new pig tail on, checked/upgraded the connections at the pin box and at the axles, same issues. Checking both the GD tech forum and the GM truck forum I see that GM is working on a fix, and most folks say that disconnecting the solar while traveling "fixes" the brake issue while traveling. Not having worked with solar, and the owner’s manual not giving me much, what is the safest way to temporarily disconnect without causing harm to the electronics and myself? Put a switch in the negative primary lead while it’s dark out with the battery disconnected??? Appreciate the help from those who have experience doing so.

[howson]

I've got a 2024 Chevy HD hooked to a 2023 303RLS. First tow (500 miles) brought a LOT of trailer brake warnings and disconnections. Put a new pig tail on, checked/upgraded the connections at the pin box and at the axles, same issues. Checking both the GD tech forum and the GM truck forum I see that GM is working on a fix, and most folks say that disconnecting the solar while traveling "fixes" the brake issue while traveling. Not having worked with solar, and the owner’s manual not giving me much, what is the safest way to temporarily disconnect without causing harm to the electronics and myself? Put a switch in the negative primary lead while it’s dark out with the battery disconnected??? Appreciate the help from those who have experience doing so.

Yep--a disconnect on the + coming from the panels to the input of the solar controller. The snip below from my master diagram shows just the solar part of my setup.

Note that a cutoff switch has DC voltage and amperage limits, so what's "OK" depends on the solar configuration of your unit. If it's a GD OEM installation a switch rated for 48vDC should be fine. AMSolar provided me with a Blue Sea 6006 which I've used in multiple locations on my 315RLTS (since none of the locations exceed 48V or 300A continuous). See https://www.bluesea.com/products/600...th__Knob_-_Red

If you search this forum you'll find lengthy debates on the subject of a cutoff switch. Some choose to use a dual (negative and positive) breaker as that is required on home solar setups that utilize PV Inverters tied to the grid. On our small DC-coupled solar setups a dual cutoff is not code-required. At least that's what the engineer at AMSolar told me--and I believe him.



Howard