"Check Trailer Wiring"

[The Alaskan Express]

Hello all - We picked up a 2022 Alliance Ave 30RLS at the end of May and have towed it almost 15k miles since on a long trip from Baltimore, MD to Nova Scotia across Canada to Alaska and back down toward TN. Along the way I have been having a lot of problems with the trailer brakes not working. I keep getting the "check trailer wiring" error on my instrument cluster. We have a 2025 Chevy Silverado 2500 LT pick up. We bought it new in 11/2024. I have cleaned all the ground points on the RV battery and 7 way cord. I cleaned the plug and checked the truck's receptacle and it appears to be OK. I also checked the connections at the wheels and made some repairs to refresh those connections. I even installed a directional diode in the 12v line to prevent back feeding the truck's electrical system and smart alternator (no help). I have asked multiple chevy dealer service advisors if there are any tech bulletins affecting the brake control system on our truck and they tell me there isn't. Has anyone else had this issue and found a solution that resolved the problem?

 

[BryanValRox]

Hello all - We picked up a 2022 Alliance Ave 30RLS at the end of May and have towed it almost 15k miles since on a long trip from Baltimore, MD to Nova Scotia across Canada to Alaska and back down toward TN. Along the way I have been having a lot of problems with the trailer brakes not working. I keep getting the "check trailer wiring" error on my instrument cluster. We have a 2025 Chevy Silverado 2500 LT pick up. We bought it new in 11/2024. I have cleaned all the ground points on the RV battery and 7 way cord. I cleaned the plug and checked the truck's receptacle and it appears to be OK. I also checked the connections at the wheels and made some repairs to refresh those connections. I even installed a directional diode in the 12v line to prevent back feeding the truck's electrical system and smart alternator (no help). I have asked multiple chevy dealer service advisors if there are any tech bulletins affecting the brake control system on our truck and they tell me there isn't. Has anyone else had this issue and found a solution that resolved the problem?

No guarantee, but you might check out this video.

 

[kmac7800]

Definitely your truck and not with your trailer. I get the same message often in my 2020 GMC Sierra.

//KMac

 

[The Alaskan Express]

I watched the video and it made me think that the current produced by the solar panel must still be back feeding through the 7 pin cord to the truck's electrical system. I am going to disconnect the same wires that he did from my controller and see if that gives me the same result. If it does, I may try adding another diode to the blue brake wire at the 7 way cord junction box and see if that stops the back feed. I do know from researching the use of one way diodes - they are primarily used to wire a tow car (dingy) to synch the car's lights to the RV lights. They recommend using a diode in all the individual tail / stop / turn light circuits. The switch approach, to me, seems like a last resort. Because I think it's important to have the solar system charging the battery so we can keep our fridge cold while we are driving between camp spots. But I do agree with the idea that working trailer brakes are more important than charging the RV battery. Thanks for the info and I will let you know how this experiment works out.

 

[M and E]

Hold off on the diode in the blue brake wire. It has to carry all your brake current, it drops some voltage, and it can mess with how the GM controller checks that the trailer is hooked up. You could trade one problem for another.

I did some digging, and this is a known GM problem, not your trailer. GM put out service bulletin 23-NA-113 on the 2024 2500/3500HD trucks. It says when the trailer battery charges higher than the truck battery, from solar or a generator, it can back-feed into the truck's trailer brake power module and shut it down. That's your "Check Trailer Wiring" message.

Bulletin 23-NA-113:
https://static.nhtsa.gov/odi/tsbs/2023/MC-10239122-0001.pdf

GM followed that with Customer Satisfaction Program N232414840, "Intermittent Loss of Trailer Brakes." The fix is the dealer replaces the Trailer Brake Power Module with GM part 85073615.

Program N232414840:
https://static.nhtsa.gov/odi/tsbs/2024/MC-11004804-0001.pdf

Yours is a 2025, so it may not show up as covered when they run your VIN. But the dealer telling you there are no bulletins isn't right. Print both of these, take them in, and push them on whether the 85073615 module fits your truck. A guy on another forum with a 2022 Duramax said that part fixed it and he leaves his solar on now

 

[Lantley]

Great follow up info M and E.
Having group discussion To exchange info is what forms are all about. Yeah we have fun and can joke and tease each other
But getting vital info through group discussion Makes the forum a valuable resource

 

[galtcity99]

I have an F150 with the HDPP package to tow. When we traded the camper they moved our pro pride hitch for us.

I had to go over a few things with them to make it right and aligned correctly.

So anyway we are all done they said take it away. I always check the breaks and lights before I get moving. Well

They pinched the wires from the break away switch while installing the pro pride hitch and my truck was having a fit ground fault and trailer fault.

I also always keep an ODB reader and use FORScan and the brake control module even thew a fault I had to clear.

Anyway after they got back from lunch they fixed that issue and we were on our way.

These new trucks are very picky about things and will disable the brake controller if there is a ground fault or something not right.

 

[2 Allies]

My former '24 3500 had to have the updated controller installed on the known issue, worked like a champ after. The issue was the solar was driving the voltage on my lithium battery above the voltage the controller liked and it would shut the trailer brakes off, the new controller took care of the issue.

 

[M and E]

My former '24 3500 had to have the updated controller installed on the known issue, worked like a champ after. The issue was the solar was driving the voltage on my lithium battery above the voltage the controller liked and it would shut the trailer brakes off, the new controller took care of the issue.

I forgot about that. It was right before one of your trips if I recall.

 

[M and E]

One thing I found out recently, only read about it though, the trailer brake breakaway switch is apparently notorious for causing voltage issues that can screw with the CanBus. Leaks voltage I guess.

 

[Maze]

It's not just a GM issue. I'm having a similar issue with a 2023 F250. Had an over the air update in August but didn't fix the issue. Now with a new 29RL its tripping the converter circuit off. Rude awakening at 0230 on our 1st shake it out trip. Carbon monoxide detector beeping, wall thermostats flashing blue, LO on display, no lights, battery totally drained. Checked the trailer breakers and that's when I suspected what was going on. More troubleshooting and a follow up with Ford next week. All of your posts and info really helps. Anyone leaning towards an Alliance wiring issue?