Issue with new 2025… trailer connection wiring issue

[dblackwell]

So, I have had my new 3500 for about 3 weeks now…. Shortly after getting the truck, I started getting a check trailer brake wiring and trailer brakes disconnected…. I haven’t pulled a trailer yet, so there isn’t an issue with a trailer, the issue is with the truck…. I used a multi meter and I have a constant hot 12v (as I should) but the parking lights pin shows a pulsating reading. Nothing else shows anything. I’ve taken the truck to the dealer and after checking the truck the believes the issue was a trailer brake control module… The part was on national back order, but they were able to get their hands on the part after stellantis got involved, but unfortunately it didn’t solve the issue. Now the dealer has the truck and seem to be at a loss and are planning on checking the connections for issues.. I’m getting less confident that they are going to get the problem resolved. Has anyone else had this issue, or are you currently having it?

 

[CdnHO]

I think your issue would be in the trailer brake circuit and not the lights. First thing I would check is to make sure all the fuses are seated correctly. Easy stuff first. Then I would look at the 7 pin connector. Have not heard of this with no trailer connected. Too much electronics in these trucks.

 

[dblackwell]

I think your issue would be in the trailer brake circuit and not the lights. First thing I would check is to make sure all the fuses are seated correctly. Easy stuff first. Then I would look at the 7 pin connector. Have not heard of this with no trailer connected. Too much electronics in these trucks.

Yes, I checked all of the fuses and I was able to push every one of them down, but that didn’t solve the issue. The seven pin has the same result in the bed and on the bumper. The dealer said they were gonna check all of the connections to see if there’s a bit pinned somewhere in one of the harness connectors, but they won’t get to that until Monday now. I saw a post on a Facebook group where someone said it was the brake controller itself on their vehicle in their own post, but I can’t get them to respond if they are talking about the controller that you can squeeze underneath the radio or the same brake controller module that my dealer been replaced that didn’t resolve the issue. I have tried to look up the Mopar part number for just that, but I can’t seem to find it.

 

[Brix316]

So, I have had my new 3500 for about 3 weeks now…. Shortly after getting the truck, I started getting a check trailer brake wiring and trailer brakes disconnected…. I haven’t pulled a trailer yet, so there isn’t an issue with a trailer, the issue is with the truck…. I used a multi meter and I have a constant hot 12v (as I should) but the parking lights pin shows a pulsating reading. Nothing else shows anything. I’ve taken the truck to the dealer and after checking the truck the believes the issue was a trailer brake control module… The part was on national back order, but they were able to get their hands on the part after stellantis got involved, but unfortunately it didn’t solve the issue. Now the dealer has the truck and seem to be at a loss and are planning on checking the connections for issues.. I’m getting less confident that they are going to get the problem resolved. Has anyone else had this issue, or are you currently having it?

I have a similar issue. I’ve had my 2025 Ram 3500 6.7 for about 3 weeks. Trailer brake service light came on probably a week after purchase. Talked to a couple dealers and didn’t get much info from them. Taking it in in a couple days to have them try to figure it out. When I’m plugged into my trailer it won’t let me adjust the trailer brake at all and I have no clue what it’s set at. Simply not working at all. Lights and blinkers work on the trailer. Also, haven’t even towed with it yet.

 

[Brutal_HO]

There's been several that reported it was the trailer brake controller (lever) at fault.

 

[stevecassel65]

So, I have had my new 3500 for about 3 weeks now…. Shortly after getting the truck, I started getting a check trailer brake wiring and trailer brakes disconnected…. I haven’t pulled a trailer yet, so there isn’t an issue with a trailer, the issue is with the truck…. I used a multi meter and I have a constant hot 12v (as I should) but the parking lights pin shows a pulsating reading. Nothing else shows anything. I’ve taken the truck to the dealer and after checking the truck the believes the issue was a trailer brake control module… The part was on national back order, but they were able to get their hands on the part after stellantis got involved, but unfortunately it didn’t solve the issue. Now the dealer has the truck and seem to be at a loss and are planning on checking the connections for issues.. I’m getting less confident that they are going to get the problem resolved. Has anyone else had this issue, or are you currently having it?

Having this problem now. The Dealer says its a known problem and has no fix for it right now. Are the kidding me. This is a brand new 90K truck

 

[HarryN]

So, I have had my new 3500 for about 3 weeks now…. Shortly after getting the truck, I started getting a check trailer brake wiring and trailer brakes disconnected…. I haven’t pulled a trailer yet, so there isn’t an issue with a trailer, the issue is with the truck…. I used a multi meter and I have a constant hot 12v (as I should) but the parking lights pin shows a pulsating reading. Nothing else shows anything. I’ve taken the truck to the dealer and after checking the truck the believes the issue was a trailer brake control module… The part was on national back order, but they were able to get their hands on the part after stellantis got involved, but unfortunately it didn’t solve the issue. Now the dealer has the truck and seem to be at a loss and are planning on checking the connections for issues.. I’m getting less confident that they are going to get the problem resolved. Has anyone else had this issue, or are you currently having it?

So I am just armchair speculating here, but there is a possible clue in that pulsating parking light voltage reading.

Perhaps some people that don't have the issue can take a measurement from their trucks and see if it shows up as a constant voltage or pulsing ?

Is there a wiring diagram for the lights posted anywhere ?

 

[dblackwell]

So I am just armchair speculating here, but there is a possible clue in that pulsating parking light voltage reading.

Perhaps some people that don't have the issue can take a measurement from their trucks and see if it shows up as a constant voltage or pulsing ?

Is there a wiring diagram for the lights posted anywhere ?

The fix for mine was the trailer brake control switch on the dash… The truck is back at the dealer.. Needs the RF shut replaced…

 

[crzysnake137]

My 2025 Big horn wioth 400 miles just displayed the Service trailer brake system message after towing my trailer for the first time, will not let me adjust the gain either as it is stuck on 7.0%. Hopefully can get this addressed

 

[RamCares]

Hi everyone, our team has been made aware of this concern. We are asking anyone who is experiencing this concern to please visit the dealer if possible so your VINs can be documented. We are also asking for private messages with your VIN and appointment information so we can offer an extra layer of assistance. Thank you!

Diamond
Ram Cares

 

[crzysnake137]

Hi everyone, our team has been made aware of this concern. We are asking anyone who is experiencing this concern to please visit the dealer if possible so your VINs can be documented. We are also asking for private messages with your VIN and appointment information so we can offer an extra layer of assistance. Thank you!

Diamond
Ram Cares

Message sent

 

[RamCares]

Message sent

Great! We will follow up with you shortly!

Diamond
Ram Cares

 

[Gunnysarg7156]

Having the exact same issue. Just purchased 2025 Big Horn with 6.7. Went through 1st 500 break in before connecting boat trailer 3 days ago. First attempt to connect trailer, no trailer lights after connecting 7 pin and turning headlights on to verify. No turn signal toe brake lights through trailer. Pull connector out, put back in several times. nothing. Shut truck off and check f30 fuse, fuse is good. Restart truck, connect everything again and bingo, all lights work. Next day, same exact process...connect, disconnect, turn headlights off/on , shut truck off and after numerous attempts, it finally recognizes a trailer is connected. FYI, boat and trailer is 2020 year model with led lighting. Also seems to be a pulsing action as the trailer lights rapidly flickers. Just spoke with Ram Care and was advised I was the first to complain about this issue. Strange thing is my son has 2023 Ram Powerwagon so we connect boat trailer to his truck and no issue 1st attempt. No pulsing trailer lights. WTF? What really sucks is that i can't even move my trailer with these issues as I can't back the trailer up with a connection as the trailer locks up.

 

[HarryN]

Having the exact same issue. Just purchased 2025 Big Horn with 6.7. Went through 1st 500 break in before connecting boat trailer 3 days ago. First attempt to connect trailer, no trailer lights after connecting 7 pin and turning headlights on to verify. No turn signal toe brake lights through trailer. Pull connector out, put back in several times. nothing. Shut truck off and check f30 fuse, fuse is good. Restart truck, connect everything again and bingo, all lights work. Next day, same exact process...connect, disconnect, turn headlights off/on , shut truck off and after numerous attempts, it finally recognizes a trailer is connected. FYI, boat and trailer is 2020 year model with led lighting. Also seems to be a pulsing action as the trailer lights rapidly flickers. Just spoke with Ram Care and was advised I was the first to complain about this issue. Strange thing is my son has 2023 Ram Powerwagon so we connect boat trailer to his truck and no issue 1st attempt. No pulsing trailer lights. WTF? What really sucks is that i can't even move my trailer with these issues as I can't back the trailer up with a connection as the trailer locks up.

They must be smoking something to say that.

 

[RamCares]

They must be smoking something to say that.

Thanks for bringing this to our attention. It sounds like you may have an open case with us, feel free to send our team a private message with your case number so we can take a further look into this for you.

Diamond
Ram Cares

 

[crzysnake137]

Just picked my truck up yesterday, the dealer
REPLACED INTEGRATED TRAILER CONTROL MODULE.

Parts
68602159AE - MODULE 1

All is working for now but will keep updated

 

[mactay]

Just picked my truck up yesterday, the dealer
REPLACED INTEGRATED TRAILER CONTROL MODULE.

Parts
68602159AE - MODULE 1

All is working for now but will keep updated

Yep,, i have brand new 2025 Ram 3500 ,, service trailer breaks comes on and no gain control,, 2nd time in the dealership,, of all the Ram trucks I've owned since the 80's,,, I can't believe this is an issue,, I can't reset it, I have to go to the dealer to get it fixed,, In the meantime time I have to drive home with no trailer breaks,, I can't believe this is an issue,, first time I hadn't evan towed anything yet, im about to go buy a cheap break controller from auto zone and just bypass that crap,,

 

[Gunnysarg7156]

Just an updated...round 2 to same dealer on 8/11. 3 hours later, engineers advised service tech it's the ITCM. No crap, told them on first service trip but they decided to reflash ECM 1st to see if that would fix it. Of course, it did not. Now it's gonna take a 3rd trip to same dealer since they didn't have ITCM in stock to replace. 10 hours, 3/4 tank diesel because dealer needed boat/trailer there both times and still awaiting a fix on $80k truck.

 

[RamCares]

Hi there, feel free to send our team a private message for an extra layer of assistance alongside the dealer.

Diamond
Ram Cares

 

[Gunnysarg7156]

Already messaged, called Ram Cares and you're useless!!! Waste of my time