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My 2020 Denali 3500 flashes the trailer lights every couple of minutes. The trailer lights seem to work as normal when driving and using the trailer. However, once parked overnight or even for a few minutes, the trailer lights flash quickly and momentarily. A quick flash of the rear trailer lights (only tail lights, not cargo lights) every couple of minutes. 

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1 hour ago, AT4 HD Ron said:

My trailer lights flash also but much more frequently!  Two different trailers and both do it - just a very quick flash when they are hooked up and truck is off. 

Had my at dealer this week, for this and a couple other small issues.

Said to be normal operation.

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I'm in the same situation. New marlon deck connected in bed via 4 pin. When I apply brakes or turn signal it disconnects to truck then works fine when I dont touch brakes or turn signal. 

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I have a trailer that I have towed for over 7 years with my 2006 duramax. I hooked new 2019  duramax to it and the only lights that work are hazards and park lights. Brakes don’t work hooked up to the 2019 either.  Power at plug. Hooked back up to the 2006 and everything works. Hooked up to my buddies 2012 Ram and everything worked.

Any ideas?

thanks

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  • 2 weeks later...
On 11/10/2019 at 11:23 PM, In2racn said:

This trailer light flicker issue concerns me... if I leave my trailer connected for a week, I risk killing the battery. Hard to believe this is "normal". 

 

 

Video of trailer lights flickering... don't mind the mutt.

Not an expert, but this might be the truck's security system just checking to make sure the trailer is still connecter to your truck.  The current flashed to the trailer wiring harness may be enough to get the LED trailer lights to flash, but not enough to light up older incandescent bulbs.  Just my guess.

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13 hours ago, Major Tom said:

Not an expert, but this might be the truck's security system just checking to make sure the trailer is still connecter to your truck.  The current flashed to the trailer wiring harness may be enough to get the LED trailer lights to flash, but not enough to light up older incandescent bulbs.  Just my guess.

That is correct

Edited by powerhaulic
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I have a 2020 Denali Duramax, I'm having issue,  when truck is off, the trailer lights stay on, first time I connected the trailer it drained my battery, then i noticed I get a pulsation on the trailer break lights.  does anyone know if this is a know issue?  Or do I have to disconnect the trailer ever time I turn off the truck?

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1 hour ago, Garett Dixon said:

I am having the same issue with my 2020 GMC AT4. I have LED lights on my boat trailer and they are not working correctly. I had no issues with my ram 3500. Did the dealership find a way to make yours work?

So I got it into the dealership a while back and they replaced the trailer light control module and it still didn’t fix anything. After that they were able to steal a receptacle off of another truck and swap it onto mine and establish that it was just a faulty receptacle. It’s worked perfectly since they replaced that. 

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  • 3 weeks later...

2020 denali hd is experiencing light issues.  Doesn't like my new marlon 2020 sled deck. Running lights will work until I hit brakes or directional. This is just the beginning of my issues as now I want to hook sled trailer to the as well. Anyone figure this out yet?

 

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On 12/21/2019 at 5:55 AM, Shredz said:

2020 denali hd is experiencing light issues.  Doesn't like my new marlon 2020 sled deck. Running lights will work until I hit brakes or directional. This is just the beginning of my issues as now I want to hook sled trailer to the as well. Anyone figure this out yet?

 

Best advice I can give you is to thoroughly read this TN https://gm-techlink.com/?p=11176

It's very important to confirm you are below the total 30amp overall load. These trucks have a very finite allowance. Typically having all LED lights proves to be the best. Since you are experiencing issues only when turn signal is on or brake applied I am thinking you are over when adding the additional amperage when braking or signaling. 

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