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2020 2500 Duramax. Is anyone else having problems with their trailer lights? I’m having problems with the lights on all but one of my three trailers. Left turn signal and brake is not working. Took it to the dealer and they gave me some bs about how the truck can’t run led lights or more than 10 amps and blew me off. So essentially my brand new truck I bought for towing can’t tow a trailer with more than two tail lights. One of the two it isn’t working on is led and one is not and it runs the led lights just fine, just not the left turn or brake on both. 

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I would think that if it works on one of your 3 trailers it's probably not the truck. I would double check all the connections and lights on the affected trailers just to make sure everything is good there. I would second guess most of the info I get from the tech's, they have led me astray before, just saying. Maybe you could hook one of your other trailers up to a friend's truck to see if the lights work, just a few suggestions.

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3 hours ago, Pfc1 said:

I would think that if it works on one of your 3 trailers it's probably not the truck. I would double check all the connections and lights on the affected trailers just to make sure everything is good there. I would second guess most of the info I get from the tech's, they have led me astray before, just saying. Maybe you could hook one of your other trailers up to a friend's truck to see if the lights work, just a few suggestions.

I’ve hooked up a couple other trucks to the trailers and they work totally fine. It’s going back to the dealership this Thursday and I’m not taking it back till I can tow a trailer. 

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I have a 2020 2500HD AT4 and so far the lights on my boat trailer are working they way they should.  I don't think I'm much help to fix your problem but I did find this info https://techlink.mynetworkcontent.com/?p=11176. The lights were pulsing when the truck was off which appears to be normal.

But now I have a sled deck in the bed of the truck for hauling snowmobiles and it uses a 4 pole connector for running tail lights, running lights, signals, and brake lights.  But all those lights will do is pulse when the truck is on and when the truck is off.  Anyone have an idea how to get the 4 pole connector in the bed of the truck working the accessory lights correctly?

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Noticed the same thing on my 2020. I have an adapter (7 round to flat 4) with the led status lights in it. When plugged into either the bumper or bed receptacle the led for the turn signals flash continuously. I don’t have a trailer with a flat 4 plug to verify but it appears the truck is looking for a signal from those before it will energize the park/running light plug. I installed a led bed light on the underside of the BAK Mx4 that has a 2 prong plug thinking i could use the in bed receptacle to power it but the park/run pin is dead. 

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  • 3 weeks later...

Truck is looking for a load before energizing the circuit.

i went thru this installing a tailgate light bar, had to tap the actual tail lights to power the light bar.

i'm betting a correctly placed resistor is what is needed.

when plugging a trailer into the truck it takes 20 seconds or so before the trailer lights actually come on

Edited by powerhaulic
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On 8/29/2019 at 12:44 AM, jprash78 said:

I have a 2020 2500HD AT4 and so far the lights on my boat trailer are working they way they should.  I don't think I'm much help to fix your problem but I did find this info https://techlink.mynetworkcontent.com/?p=11176. The lights were pulsing when the truck was off which appears to be normal.

But now I have a sled deck in the bed of the truck for hauling snowmobiles and it uses a 4 pole connector for running tail lights, running lights, signals, and brake lights.  But all those lights will do is pulse when the truck is on and when the truck is off.  Anyone have an idea how to get the 4 pole connector in the bed of the truck working the accessory lights correctly?

Also have a 2020 AT4 and Marlon Xplore Pro II sled deck with the rear light bar... Hoping we can come up with a fix before snow flies... 

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19 hours ago, Basketcase said:

Also have a 2020 AT4 and Marlon Xplore Pro II sled deck with the rear light bar... Hoping we can come up with a fix before snow flies... 

My truck is at the GMC dealership while I'm on vacation this week so they can try and figure something out.  I don't have high hopes.  I should add that the sled deck lights work perfect when we also have our Malibu boat trailer connected to the 7 pin on the bumper.  I have a Full Lotus deck.

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On 8/24/2019 at 4:28 PM, Jordan94 said:

2020 2500 Duramax. Is anyone else having problems with their trailer lights? I’m having problems with the lights on all but one of my three trailers. Left turn signal and brake is not working. Took it to the dealer and they gave me some bs about how the truck can’t run led lights or more than 10 amps and blew me off. So essentially my brand new truck I bought for towing can’t tow a trailer with more than two tail lights. One of the two it isn’t working on is led and one is not and it runs the led lights just fine, just not the left turn or brake on both. 

 

I doubt it is the fuse, but something in that trailer lighting wire circuit because the trailer left turn signal and trailer brake lights use the same fuse #73.

 

Fuse1.thumb.jpg.47ea78f1b973c25e01af186ab5635c96.jpg

 

 

Fuse2.thumb.jpg.db4957e4106dceb08a396b661461e2e8.jpg

 

 

Fuse3.thumb.jpg.3faaa3459ea216c7d5cd3ccbbee6cbb9.jpg

 

 

Fuses.jpg

Edited by SkidooSteve12
Added larger separate pictures
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