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Discussion Starter #1
I recently completed a 5000 plus mile road trip pulling a trailer about 3000 of those miles. 3 different trailers...

I checked several times to be sure the lights were working throughout the trip. When I arrived home while backing the trailer into my driveway, my wife noticed the right side was out. I assumed it was the trailer wiring not the truck. I has been 3 weeks since but I had some time today and started trouble shooting the trailer wiring. My first step was to plug it into another vehicle because I dropped the canyon off at the dealer for the first oil change and some minor warranty work (steering wheel not aligned and the rear charge port not working).

Well, I plugged the trailer in and all the lights worked just fine. Anyone have any problems with their trailer circuits not working correctly? The truck is still at the dealer and probably will be until the end of next week. I'd check the fuse but I cant for that reason.

Any thoughts?
 

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Running lights or turn signals? If it's the running lights that aren't working then it's 100% the trailer since that's all one circuit on the truck.

When you get your truck back, The 7 pin has the wiring diagram on the cover. Use a multi meter and test your 7 pin.

99% of the time, it's the trailer not the truck.
 

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Funny, I had my trailer lights act up on my last night. My truck gave me an error "check trailer wiring" my running lights were not working but my turn/stop lights were working.

Pulled out the multi meter and I had power at the 7pin on the truck, plugged in the trailer and backprobed the plug and had power so I started looking for where I no longer had power, working from the first light toward the tongue and then they started working on their own.

The truck was intelligent enough to know I had a short in the trailer wiring, and I'm sure you've noticed if you unplug the trailer it will tell you so.
 

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I need to check my trailer wiring. I haven't had a chance to check my wiring yet, maybe tonight. Anyways though, mine does something like this too. I have 4 amber marker lights on the trailer, 2 on the sides that you can't see in your mirrors when looking back, and then 2 on the wheel wells that you can see when looking in the mirror (which are farther back behind the 2 on the sides), and then the brake lights at the rear. The 2 side marker lights work all the time. 1 of the wheel lights quit a while ago. It did, however, come back on for one trip, but then quit again. Then, the other wheel light quit a couple weeks ago. And now, my right rear brake light has also quit.

I figured its just faulty wiring or bad lights. I didn't think it would be wiring though, as the marker lights closer to the truck are still working, and also my left rear brake light works as well. I don't know how the wiring runs under the trailer, so I am just assuming that the first lights in the run are the closest to the truck, but who knows. I also thought that it was just faulty lights, since it's not everything. I would find it odd that just a few of my lights are out because of some plug issue on the truck.
 

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Ended up being a blown fuse. I suspect the live lead grounded when it got wet. I went back and soldered every connection and wrapped them with heat shrink. No problems since then. I now keep spare fuses in the glove box which pretty much guarantees I will never need them.
 

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Ended up being a blown fuse. I suspect the live lead grounded when it got wet. I went back and soldered every connection and wrapped them with heat shrink. No problems since then. I now keep spare fuses in the glove box which pretty much guarantees I will never need them.
I had the same problem... Dealer said turn the light switch to the off position or turn the truck off when hooking up the trailer wiring. I just turn the light switch to the off position, have never had a problem since.
 
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