mjonesjr84

That is correct. The truck only activates the module when it detects something plugged into the 7-pin plug. That is why the module has to be plugged in before the 7-pin.

For those who have the GM trailer TPMS installed in a trailer and the tires/wheels are more than 25' away from the license plate (where the sensor receiver is at), here is a simple modification to make your sensors rear correctly and not give you the "Check Trailer TPMS" warning. This should work on any 2020+ truck. My trailer has a 40' deck, not counting the gooseneck. The truck would hit or miss connecting to the TPMS in the trailer tires. Here is the parts list: OEM style connectors https://www.amazon.com/dp/B0C3VY14MG?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1 3 Pin connector https://www.amazon.com/dp/B0BGQ28631?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_42 18 AWG wiring (3 conductor) https://www.amazon.com/dp/B09YDMGL2M?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_4&th=1 Remove the license plate and pop the sensor off the bracket and unplug it. I fished about 5' of the wire down through the rubber plug down to the location where the receiver is mounted. Build a female end pin out with the OEM style connectors and plug it into the factory wiring harness. On the end that runs down from the rubber plug in the bed, put one of the 3 pin plugs on the end of the wire. I used these connectors here since they are easier to disconnect by hand. Now run your wire on your trailer. I started at the 7-pin plug and ran it back to where I was mounting the GM receiver. I followed the GM rear trailer camera wiring. Now build a male OE style plug on the end of the wire. Mount the receiver and plug it in. **Make sure when you plug in your trailer to the truck, the receiver gets plugged FIRST then the 7-pin plug. When unplugging, the 7-pin FIRST and the receiver last. Plugging in the 7-pin triggers the truck to activate the receiver. Finally, plug everything in and test the system. I went through the steps to relearn the trailer TPMS. I knew instantly that it worked because of how fast the truck picked them up.

Kinda my thoughts as well. I ran the wires, which are encapsulated in a vinyl jacket, on top rear of the front axle tube secured with zip ties.

Yes I changed both. The factory wires ran across inside each axle tube.

My wiring had a blue and white from the main harness. I started there with both blue and white 10AWG to each brake.

1000%. I actually got mine fixed yesterday and not by the dealer. I spent 30 minutes under the trailer testing each magnet (6) resistance. When they checked good, I decided to rewire the brakes from where the blue wire comes out of the harness at the axles. I eliminated each individual crossover in the axles with 1 cross over. I used 10AWG wire. Hooked the truck up, tested the brake switch in the driveway and got no disconnect. So I hooked the trailer up and drove it about 10 miles across town and back with no issues. 6 trailer brakes with a truck/trailer weight of 24k is nice. I don't understand why it would disconnect in my 25 but not my brothers 22. I can't believe GM hasn't been sued for a wreck. Even if there is an issue, an old fashioned trailer brake controller would still power through and work.

I emailed you a message this morning regarding my truck disconnecting the trailer brakes. This is a major safety issue that I need help getting fixed.

No. I talked to Hydrastar and they recommended their module for the electric drum brakes, even the dealer printed off a GM recommendation for the Hydrastar modules.

Magnetic drum brakes.

My brother's 21 and 22 3500s that he owns doesn't do this with my trailer.

If I restart the truck, the brakes will come back on until I use them again. My trailer TPMS sensors keep going in and out as well.

Yea that's different. I've read the new Rams have the same problem. I hate the Ford interior.

Didn't work for mine. I installed the hydrostar modules on both the 12 volt positive and the brake wire as suggested by hydrostar and my GM dealer. When I left this past Wednesday for an 8 hour trip with the trailer RV still did the brake disconnection went hard on the brakes, when I needed them the most. I forgot the 2022 module that I have at home or I would have swapped that in. There is zero reason for the brakes to disconnect. Even if there is a problem with the trailer brakes the truck shouldn't disconnect. I see it as a major safety issue.

I have a LiFePO4 battery on my crawler hauler. I talked to HydraStar and bought their recommended modules. We shall see how it works next week. I also have a '23 TBCM that is new in the box to go in as well. Hopefully the HydraStar modules work and I can send. It back.

Did the '21 module work on your 2025? I have a module for the '19-23 models that is NIB.

I sent you an email. My dealer told me everything is working fine per their tester on my truck. I know it is not.

They told me their tester showed everything operating normally. They said they would need the truck with the trailer to do any further testing and started to play it off on 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.

I installed the Hydrostar module on the brake wire (blue) and prepped the 12v+ wire module in case it needs it. Hydrostar said I may or may not need the module on the 12v+ between the truck and trailer. I also bought a GM 23306694 brake control module from the '19-'23 trucks that don't seem to have the issue. I found it on eBay for $45 shipped NOS. I've read this was a direct swap and solved the issues. I'm not going to swap this in until the dealer looks at the truck Monday or the modules don't fix the issue. I am still going to take the truck in on Monday to have GM start looking at it.

Perfect. The Hydrostar module is just a diode so I'm going to install one that I have to see if that works.

Just to confirm, the blue brake wire from the truck to the junction box with flow towards the trailer? I'm going to try that before ripping the emergency battery out and rewiring the emergency brakes.

I have thought about removing it and using the onboard LiFePO4 battery. Does the diode go in the power wire feeding the emergency battery or the blue brake wire?

I've seen that. I'm not running EOH, just the standard electric brakes. I've thought about installing a diode in the brake wire to see if that works.

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

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.