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Discussion Starter #1
Hi, I have a 2018 GMC Denali and would like to know if anyone has a 7 blade trailer connector wiring diagram. I'm making a 2' extension of a 7 blade male to a 7 blade female connector. Thanks, Ray
 

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No problem! Same to you...


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For the future you can just google/internet search just about anything including the 4, 5, 6, 7 wire plug wiring male and female, also all trouble codes what they mean and possible solutions.
No waiting for responses, what we refer to DIY searching for solutions on the internet.
 

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Discussion Starter #6
For the future you can just google/internet search just about anything including the 4, 5, 6, 7 wire plug wiring male and female, also all trouble codes what they mean and possible solutions.
No waiting for responses, what we refer to DIY searching for solutions on the internet.
Did that..... been there. I "always" do a search. I couldn't find anything positive therefore, I asked my friends here on the forum and they pulled through within minutes. I love real world users........ Ray
 

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Discussion Starter #8 (Edited)
A little snappy for a person looking for help
7 pin trailer wiring found this in less than 20 seconds, obvious you didn’t try very hard.
Real world users always searches before jumping on forums.

https://www.bing.com/images/search?...386F1423559A6335FAB8A61A2&FORM=IQFRBA&PC=APPL
You're ridiculous...... PERIOD! What's snappy about me? You're the one that wants to be argumentative over nothing. I saw all the diagrams "before" my O.P. I've never read ANY of your posts but, I bet you could have found answers good/bad by googling as well. I trust the people on this forum and look for true real world answers from them simply due to owning these trucks. I asked for a wiring diagram on a 2018 GMC, I didn't come across anything that was definitive to my 2018........ So I asked..... BIG DEAL. If I had the truck on hand, I would have simply checked out the harness adapter on the truck with my meter. I was simply looking for a quick positive answer in order to make up an extension due to being pressed for time.
In 14 minutes M.A.M. posted a pic of the diagram..... He is a perfect example of the folks here that I sincerely appreciate.

My best experience on this forum was to return the help that was given back to me from the members here. Like many here, back in 2014 I had headlight problems with my 2015. These real world owners helped me out which was priceless...... In return, after I did my H.I.D. install, I posted back my install with pic's found here in post #60. http://www.duramaxforum.com/forum/2011-2016-non-powertrain/542305-2015-sierra-hid-install-6.html
Why?? Because I appreciated everything those members helped me with on that install. Everyone either asked for help or were more than happy to give it. "That's what this forum is about"......... Man am I glad I "Googled/Internet" and found this forum years ago!:wink2:
 

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No need to search for vehicle and year specific. Trailer wiring is standard across the industry. The only time you'd find otherwise is if someone wired a trailer their own way
 

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Discussion Starter #10
No need to search for vehicle and year specific. Trailer wiring is standard across the industry. The only time you'd find otherwise is if someone wired a trailer their own way
I wasn't sure about that..... As the old saying goes "You learn something everyday" Thank you! :smile2:
 

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I just went to this thread, got as far as the picture,and printed it. Then scrolled down, and saw the search. Almost got worried, then seen round,spade several types wired differently. I’m 70 and have a box of different connectors, so I see where the original poster could be confused. I am new to the diesel world but not to power/electrical systems. Being old I have learned.
 

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What M.A.M. posted and what I posted is the way these 4, 5, 6, 7, pins have been wired since the 60's, that I know of anyway.
Like PHAT RAT said standard in the industry unless someone else had a different idea on their own trailer.
Nothing to be confused about as long as you understand basic color code wiring.
 

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I’ve seen various trailer manufacturers use different/their own color coding, but the position of the lighting function doesn’t change. That can mess with you if you’re not careful...


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Discussion Starter #14
I’ve seen various trailer manufacturers use different/their own color coding, but the position of the lighting function doesn’t change. That can mess with you if you’re not careful...


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You're absolutely right..... you never know about proper color codes being used. I've come across it too many times. I.M.O., the best way is to confirm proper connections is by using a 6v - 12v circuit tester. In my case, I was simply looking for a quick/positive answer without my truck at hand. Thanks again for your help. Ray :smile2:
 

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Discussion Starter #15
I just went to this thread, got as far as the picture,and printed it. Then scrolled down, and saw the search. Almost got worried, then seen round,spade several types wired differently. I’m 70 and have a box of different connectors, so I see where the original poster could be confused. I am new to the diesel world but not to power/electrical systems. Being old I have learned.
Exactly..... I knew if I asked in this forum I would get a correct answer. This forum rocks........:brian
 

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I just went to this thread, got as far as the picture,and printed it. Then scrolled down, and saw the search. Almost got worried, then seen round,spade several types wired differently. I’m 70 and have a box of different connectors, so I see where the original poster could be confused. I am new to the diesel world but not to power/electrical systems. Being old I have learned.
You have to remember when your looking at the plug the wire location is the opposite when looking at the plug and the wire location on the back side.
The center has always been for reverse/backup lights on a 7 wire plug.
I have to think about it every time I'm connecting wires, the trailer male plug terminals is the opposite location of the female vehicles plug.

If you had a 7 wire plug that the center was for charging then someone changed the location, that's not the standard.
7 wire plugs are blades that's all I've ever seen, with the center (backup lights) is round, the 6 wire plugs are round and the center is black for 12 volt.
 

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Discussion Starter #17
You have to remember when your looking at the plug the wire location is the opposite when looking at the plug and the wire location on the back side.
The center has always been for reverse/backup lights on a 7 wire plug.
I have to think about it every time I'm connecting wires, the trailer male plug terminals is the opposite location of the female vehicles plug.

If you had a 7 wire plug that the center was for charging then someone changed the location, that's not the standard.
7 wire plugs are blades that's all I've ever seen, with the center (backup lights) is round, the 6 wire plugs are round and the center is black for 12 volt.
Great point! Ray
 

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Yeah, I’ve pulled trailers that are wired with a 7 round. Keep an adapter pig tail on the truck. @phat rat Can I use your trailer? Haha


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I'll refrase that, 7 pin with blades is all that I've seen and worked with.
I did come across these during this discussion, but I think they are not easy to come by anymore.
I'm pretty sure you won't find 7 pin round on any vehicles as standard trailer wiring on vehicles from the factory these days.
 
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