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2025 Ram 3500 7 Pin Receptacle Issue

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B-Lake

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Hello!

I just purchased a 2025 Ram 3500 to haul a 5th wheel we purchased.

Got to the dealer to haul it home and when we connected the unit to the 7 pin receptacle there were no lights! The service tech got the multimeter and said there is no power at plug.

So, i took the truck to a ram dealer and they hooked it up and diagnostics showed there was an update needed.

Code was cleared, headed back to RV dealer thinking I would connect and be good to go! But after connecting, no power to the lights. Used another truck in the lot to connect to the trailer, lights worked.

Grabbed the multimeter again and the plug had power, 12.7 volts with the engine off, and 14v with the truck running.

The one peculiar thing is, when we checked the other pins on the receptacle, the reverse lights had a voltage fluctuation.

I’m wondering if this could be a ground issue causing the entire issue.

To compound the issue, all this is taking place 10 hours away from the house.

Any help or thoughts would be greatly appreciated.
 
B-Lake: first thing that I'm thinking is fuses and making sure they are all seated properly.
You said you put a meter on the receptacle and had voltage running and not running you checked all the other pins and had turn signals ; brake lights and running light's??
Did you add a temporary ground between the truck and the trailer?
 
Tims Ram said:
B-Lake: first thing that I'm thinking is fuses and making sure they are all seated properly.
You said you put a meter on the receptacle and had voltage running and not running you checked all the other pins and had turn signals ; brake lights and running light's??
Did you add a temporary ground between the truck and the trailer?
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yes, the fuses is the first thing i did…..crazy thing is….75% of the fuses weren’t fully seated!

That’s a great idea on the temporary ground!
 
My 2025 is in the shop right now for the same plus it has a weird surge when coming to a stop. I installed my additional reverse lights from my 22 to the 25 to find no power on the reverse wire. The center pin at the trailer connector has no power, other pins seem to be fine. Other posts are saying faulty trailer control modules. I’ll update when the dealer figures it out. They told me they are in talks with engineers at Chrysler over both issues and to plan on being in the loaner for the week. Not happy since I just bought the truck.
 
I posted this yesterday on the 1500 forum before I realized there was an HD forum. A somewhat similar issue to B-Lake's lighting issue with a potential solution.

Issue:

2025 RAM 2500 with problem starting the first time I connected the trailer (300 miles on the truck). All trailer lights work fine when testing with ignition OFF. When I turn on the ignition, either starting the engine or not, the running lights either blink or go off. Turn the ignition off, and the running lights come back on. All other trailer lights work fine and all lights on the truck work fine. All trailer lights are LED.

What I've done:

1. Dealer trip: the dealer stated nothing wrong, but at the time, I hadn't realized the problem only occurs when the ignition is on. I believe they only tested with the truck off.

2. I tested the truck with an old school test lamp. Same occurrence: test lamp on with ignition off but off with the ignition on. I also tested with a voltmeter and got fluctuating voltages like B-Lake, but I am not confident the voltmeter is good.

3. I checked all trailer wiring and brakes. All good.

4. I removed and reset the 7-pin connector behind the bumper.

5. Fixed? I used the trailer auto lights check function on the truck with the ignition on. This seems to have reset the output, and all lights are now working. Hopefully they will continue to work for me, but it may be an intermittent issue.
 
jake2544 said:
My 2025 is in the shop right now for the same plus it has a weird surge when coming to a stop. I installed my additional reverse lights from my 22 to the 25 to find no power on the reverse wire. The center pin at the trailer connector has no power, other pins seem to be fine. Other posts are saying faulty trailer control modules. I’ll update when the dealer figures it out. They told me they are in talks with engineers at Chrysler over both issues and to plan on being in the loaner for the week. Not happy since I just bought the truck.
Click to expand...
Any update from you dealer trip? Have the same issue on my ram3500. Just bought a truck camper and marker lights are off. Hooked up 7pin to standalone battery and lights turned on. Also noticed that lights on the camper would light up momentarily when locking or unlocking the truck. Greatly appreciate any info you can share. Thanks in advance.
 
I'm also having similar intermittent issues with my '26. It wasn't working for marker/running lights, but did have brake and signals. Left and came back to the camper and it was working fine. Hopefully you guys get a resolution so I can use that when/if I have to take it into the dealer for this.
 
Any updates on this? I have a truck camper in the back of my 2025 3500 DRW with the 5th wheel prep and the running lights on the camper aren't working, only work for a few minutes (until the truck tells me there's an issue with the "turn signal" circuit that doesn't exist), or just flash randomly with the key. Tried the usual suspects. Camper lights are fine.
 
The dealer replaced my brake control module. Hook up at home tested fine. I will update once I tow again. Hopefully this fixed the problem.
 
Mississippi Ram said:
Did that fix the issue?
Click to expand...
It doesn't appear to have fixed it. I brought the RV in for service to ensure it is not the trailer, but I seriously doubt it is the trailer wiring as I tested all of that myself. I'll be taking the truck back into the dealer soon.
 
Ok, Im having the same issue with my livestock trailer. I have a switch to turn on the interior lights and when they are switched on, they flicker the whole trailer. (LED lights btw). I also went through and tested everything and the fuses and I’m still having the same issues.

I have been told that the tech will have to talk to Chrysler for a fix and that this is a “ rare issue”.
 
Mississippi Ram said:
Ok, Im having the same issue with my livestock trailer. I have a switch to turn on the interior lights and when they are switched on, they flicker the whole trailer. (LED lights btw). I also went through and tested everything and the fuses and I’m still having the same issues.

I have been told that the tech will have to talk to Chrysler for a fix and that this is a “ rare issue”.
Click to expand...
My trailer is LED too. I hope they find a fix soon. It is very frustrating to not be able to tow at night without constant warning beeps and flickering lights.
 
I have an appointment with the dealer tomorrow. I will have to leave it for a few days. If I don’t respond on here after a week, shoot me a reply.
 
Prometheus said:
My trailer is LED too. I hope they find a fix soon. It is very frustrating to not be able to tow at night without constant warning beeps and flickering lights.
Click to expand...
Dealership has an official fix “ Trailer module replacement” it is now a recall and under warranty. God is Good

Hope this helps you!
 
Mississippi Ram said:
Dealership has an official fix “ Trailer module replacement” it is now a recall and under warranty. God is Good

Hope this helps you!
Click to expand...
Thanks for the info and happy that this is a recall. I was getting pretty frustrated. The RV checked out fine at the dealer. Same issue with the lights on the way home. I purchased a 7-pin test plug, and it all checks out, so figure if I brought it to the dealer, they would find the same, that nothing apparently wrong. I still have the same issue, everything works fine with the engine off, as soon as I start the engine, the trailer running lights start flickering, indicating a truck issue. I unplug the trailer, plug in the test unit, and everything is fine, indicating a trailer issue (did this 3 times). I will call the dealer and ask about the trailer module recall on Monday! That will be the third safety recall in the first 7 months of ownership.

I just found the recall information online. It looks like it will be posted on the NHTSA website on 10 Feb 26.
 
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Another recall? Will hate to take it in as my lights work perfectly towing the 5th wheel. Heck, as soon as I plug it in the truck, the lights go on a self test routine and don't need my bride walking around checking while I sit in the truck.
 
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