Trailer wiring not working

WalleyeMikeIII

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This was good advice. The first thing that I had plugged in was my boat trailer and after seeing that the lights were not working, grabbed the 7pin tester to see that only one of the lights was on. This was with headlamps on, hazards blinking, etc. I ran home to grab my other car and had no issues with the trailer lights which led me to believe there was an issue. After reading your posts last night, I decided to fiddle with it some more and borrowed my neighbor's trailer as a test. Sure enough, they lit up just fine behind the Yukon. It seems there is something going on between my boat trailer and the Yukon; perhaps the load from the LEDs is not sufficient to engage the module. Oddly not an issue with with my other car's 7pin plug.

For those that stumbled upon this post in the future and are experiencing the same issues, it seems that a 7pin test plug will not draw enough for the T1s to engage the module. Suggest plugging in a trailer with incandescent bulbs to test functionality.
FWIW, my Boat trailer has all LED Lights, and works fine w/ my Factory 22 Denali w/ Max Tow right "out of the box" (meaning there was no need to do anything other than plug in the 7 wire connector on my trailer to the vehicle.
 

DenaliCountry

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FWIW, my Boat trailer has all LED Lights, and works fine w/ my Factory 22 Denali w/ Max Tow right "out of the box" (meaning there was no need to do anything other than plug in the 7 wire connector on my trailer to the vehicle.
My Enclosed snowmobile trailer has all LEDs and works also with no issues out of the box.
 

Fless

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Makes me wonder if there's a calibration or firmware to correct the sensitivity.
 

Chad G 1979

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If the trailer in question has a bit of a high impedance in the ground circuit, it could possibly throw off the module a bit in the vehicle…and maybe cause it to shut down…I’d check connections everywhere in the trailer.
THIS right here. I had to borrow my FIL trailer and truck to haul some wood and dirt for my yard, and the lights wouldn't work on the trailer. his 19 silverado can tell when it is hooked up. We spent about 30 minutes trying to get it to work, and since it was daytime i drove it home and by the time i got home, they were working. I spent 50 bucks to install new lights and wiring on the trailer as i couldn't figure out what the issue was until I went to change out the grounding wire. It is attached under the plate for the tongue jack. when i removed the bolts for the jack to replace the wire, it was all rusty and the bolts were snug, but not tight. so i removed the jack and cleaned up the frame to a nice metal surface and hooked up the new ground wire and, voila, it worked as soon as i plugged it in the truck knew it was there. also hooked it up to my canyon and acadia and on both, the lights came up instantly. I would double check your grounding wire to make sure it has a good connection to the trailer, and any other places the wiring may be grounded to trailer. If the grounding is funky, your wiring loop isnt closed so the vehicle won't sense it is there.
 

Fless

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THIS right here. I had to borrow my FIL trailer and truck to haul some wood and dirt for my yard, and the lights wouldn't work on the trailer. his 19 silverado can tell when it is hooked up. We spent about 30 minutes trying to get it to work, and since it was daytime i drove it home and by the time i got home, they were working. I spent 50 bucks to install new lights and wiring on the trailer as i couldn't figure out what the issue was until I went to change out the grounding wire. It is attached under the plate for the tongue jack. when i removed the bolts for the jack to replace the wire, it was all rusty and the bolts were snug, but not tight. so i removed the jack and cleaned up the frame to a nice metal surface and hooked up the new ground wire and, voila, it worked as soon as i plugged it in the truck knew it was there. also hooked it up to my canyon and acadia and on both, the lights came up instantly. I would double check your grounding wire to make sure it has a good connection to the trailer, and any other places the wiring may be grounded to trailer. If the grounding is funky, your wiring loop isnt closed so the vehicle won't sense it is there.

An easy way to test the ground is to connect a battery jumper cable to good grounds on both the truck and the trailer. Bypass or add to the wired ground temporarily.
 
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DenaliCountry

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THIS right here. I had to borrow my FIL trailer and truck to haul some wood and dirt for my yard, and the lights wouldn't work on the trailer. his 19 silverado can tell when it is hooked up. We spent about 30 minutes trying to get it to work, and since it was daytime i drove it home and by the time i got home, they were working. I spent 50 bucks to install new lights and wiring on the trailer as i couldn't figure out what the issue was until I went to change out the grounding wire. It is attached under the plate for the tongue jack. when i removed the bolts for the jack to replace the wire, it was all rusty and the bolts were snug, but not tight. so i removed the jack and cleaned up the frame to a nice metal surface and hooked up the new ground wire and, voila, it worked as soon as i plugged it in the truck knew it was there. also hooked it up to my canyon and acadia and on both, the lights came up instantly. I would double check your grounding wire to make sure it has a good connection to the trailer, and any other places the wiring may be grounded to trailer. If the grounding is funky, your wiring loop isnt closed so the vehicle won't sense it is there.
Agreed with both. The other thing to look at is the nose on the 7 PIN. On my 2019, I had issues with my trailer intermittently not connecting to the truck which caused the lights to stop working. Turns out the nose on the trailer side 7 PIN was just a hair too long which created a bad ground. Changed it out to a 7 pin with one that had a shorter nose on it and they worked perfectly. So in this case, it may not be the truck but the trailer side causing the issue. Something to look at anyway.
 

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