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Discussion Starter #1
Just bought a 2020 GMC 2500hd AT4, and am having an issue with trailer lights not working.

Truck is not detecting the trailer. I have a 5 pin from the harness to a 7pin adapter (new and old adapter have been tried). No brakes are installed on the trailer, that wire is not grounded but is terminated. Trailer lights work when connected to my Yukon.

Trailer has 4 led running lights and 2 led tail lights. Am I not pulling enough power to activate the trailing app? I have had several suggestions add lights, add resistors, try a lamp out bypass adapter.

Any ideas/ solutions?
 

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I had the same Issue - your plug may not be seating in the socket. Feels like it is but it isn’t.

Wiggle and tickle it while pushing it in. Needs another 1/4” to connect.

Plug design slimmed down slightly in the Recent past and they don’t jive so well anymore.

Don’t use spray lube it may short or ground out the brake circuit and good luck finding that fuse.

Anyway that’s what I found in my case.

I'm not allowed to edit to add more info for some ridiculous reason but you may find the plug is swimming around in the socket, feels like its connecting but it isn't fully. So keep at it.
 

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LHN...We ARE the Joneses
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3 vertical dots on the upper right side of your post, drop down menu has 'edit' option to select.
(posts merged ;) )
 

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LHN...We ARE the Joneses
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....for some ridiculous reason.
Discovery....can be fulfilling. :LOL:
I've seen those pop up in posting....waited a few seconds and then went forward.

But not on editing....and.I do a lot of editing.
I think my left and right side brain are merging.....left hand keystrokes swap with the right hand, and vice-versa.
Can't decide if I need more Drugs, or less. :ROFLMAO:
 

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Only allowed 7 edits in a specific amount of days is the pop up I get.. With my appalling typos and sentence structure it doesn't jive so well.
 

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Just bought a 2020 GMC 2500hd AT4, and am having an issue with trailer lights not working.

Truck is not detecting the trailer. I have a 5 pin from the harness to a 7pin adapter (new and old adapter have been tried). No brakes are installed on the trailer, that wire is not grounded but is terminated. Trailer lights work when connected to my Yukon.

Trailer has 4 led running lights and 2 led tail lights. Am I not pulling enough power to activate the trailing app? I have had several suggestions add lights, add resistors, try a lamp out bypass adapter.

Any ideas/ solutions?
Go read the Feb. 27th issue on GM Techlink concerning the trailering app and lights problems. Maybe it will get you going.
 
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