2017 GMC Canyon "Check trailer wiring" warning

F

fcpfour

Newbie
Hi all — First time poster here. I will try to be brief, but it will be a challenge. I bought a 560 Ultra #541 from the original owner in spring 2025. I tow it with a 2017 GMC Canyon with a trailer towing package. Within an hour of picking up the trailer (and on my way to Camp Inn headquarters, I was getting a warning message from my truck, "Check Trailer Wiring." The kind folks at Camp Inn installed a new 7-prong plug and harness, adjusted the brakes, replaced some bulbs, checked the wiring, and gave the camper a general going-over. On my way home from WI to OH the "warning" light/chime issue continued (sometimes incessantly) even with the newly installed plug. Camp Inn then suggested a 7-prong Lamp-Out LED Bypass between truck and trailer to increase the resistance as maybe my truck was not recognizing the low draw of the LED trailer lights. (I was unable to use the trailer last year.) But this past weekend I headed out for my maiden camping trip. The "Check Trailer Wiring" problem persists, again sometimes incessantly. The Bypass Adapter has not helped. All lights work. In my online research to date it seems the general consensus is that if the truck only warns me when the trailer is attached then the problem is in the trailer, not the truck. The camper has a ZAMP Solar panel, installed by the original owner. Some online "experts" claim the solar panel may be "overcharging" and confusing the sensors in the truck. My electrical diagnostic skills are pretty rudimentary. Any help would be appreciated ... especially if anyone here has experienced this issue with a GM truck like mine. Thx.
 
fcpfour said:
Hi all — First time poster here. I will try to be brief, but it will be a challenge. I bought a 560 Ultra #541 from the original owner in spring 2025. I tow it with a 2017 GMC Canyon with a trailer towing package. Within an hour of picking up the trailer (and on my way to Camp Inn headquarters, I was getting a warning message from my truck, "Check Trailer Wiring." The kind folks at Camp Inn installed a new 7-prong plug and harness, adjusted the brakes, replaced some bulbs, checked the wiring, and gave the camper a general going-over. On my way home from WI to OH the "warning" light/chime issue continued (sometimes incessantly) even with the newly installed plug. Camp Inn then suggested a 7-prong Lamp-Out LED Bypass between truck and trailer to increase the resistance as maybe my truck was not recognizing the low draw of the LED trailer lights. (I was unable to use the trailer last year.) But this past weekend I headed out for my maiden camping trip. The "Check Trailer Wiring" problem persists, again sometimes incessantly. The Bypass Adapter has not helped. All lights work. In my online research to date it seems the general consensus is that if the truck only warns me when the trailer is attached then the problem is in the trailer, not the truck. The camper has a ZAMP Solar panel, installed by the original owner. Some online "experts" claim the solar panel may be "overcharging" and confusing the sensors in the truck. My electrical diagnostic skills are pretty rudimentary. Any help would be appreciated ... especially if anyone here has experienced this issue with a GM truck like mine. Thx.
Click to expand...

I'm guessing here --- throw a blanket over the solar panel to shut out all the light. Run your ligths and fan for an hour or two...this should bring the battery voltage down to 12.6 vollts or so....you can see the voltage on the LED display on the right hand side of the gally....

Plug in the canyon --- see if the problem continues. This will at least tell you if the canyon isn't happya bout the 'high voltage'
 
fcpfour said:
Hi all — First time poster here. I will try to be brief, but it will be a challenge. I bought a 560 Ultra #541 from the original owner in spring 2025. I tow it with a 2017 GMC Canyon with a trailer towing package. Within an hour of picking up the trailer (and on my way to Camp Inn headquarters, I was getting a warning message from my truck, "Check Trailer Wiring." The kind folks at Camp Inn installed a new 7-prong plug and harness, adjusted the brakes, replaced some bulbs, checked the wiring, and gave the camper a general going-over. On my way home from WI to OH the "warning" light/chime issue continued (sometimes incessantly) even with the newly installed plug. Camp Inn then suggested a 7-prong Lamp-Out LED Bypass between truck and trailer to increase the resistance as maybe my truck was not recognizing the low draw of the LED trailer lights. (I was unable to use the trailer last year.) But this past weekend I headed out for my maiden camping trip. The "Check Trailer Wiring" problem persists, again sometimes incessantly. The Bypass Adapter has not helped. All lights work. In my online research to date it seems the general consensus is that if the truck only warns me when the trailer is attached then the problem is in the trailer, not the truck. The camper has a ZAMP Solar panel, installed by the original owner. Some online "experts" claim the solar panel may be "overcharging" and confusing the sensors in the truck. My electrical diagnostic skills are pretty rudimentary. Any help would be appreciated ... especially if anyone here has experienced this issue with a GM truck like mine. Thx.
Click to expand...
We have a 2024 Toyota Land Cruiser and I sometimes get random “Trailer Disconnected” messages. Our trailer’s 7pin has seen better days and we planned to replace it, hoping that might clear the “disconnected” issue. Reading your post I’m not as optimistic…
 
Sweeney said:
I'm guessing here --- throw a blanket over the solar panel to shut out all the light. Run your ligths and fan for an hour or two...this should bring the battery voltage down to 12.6 vollts or so....you can see the voltage on the LED display on the right hand side of the gally....

Plug in the canyon --- see if the problem continues. This will at least tell you if the canyon isn't happya bout the 'high voltage'
Click to expand...
Sweeney — I like your thought of blocking the light to the solar panel. Problem is the "check trailer wiring" light usually doesn't start chiming until 45 to 60 minutes into my drive. I think the blanket would blow off by then. :) Hah! But maybe I can rig up some sort of cover that would stay attached while driving. I am going to try this. Wish the solar panel (which is zip-tied on top) had an on/off switch so that I could easily take it out of the equation, but alas, no.
 
I have a 2018 Colorado and used to get the warning when driving. I never figured it out because it came and went. Then my cabin lights quit working and with the help of Craig and Cary we found my cabin lights had a bad ground. I was able to use the ground from the running lights to fix the problem. It was months later when I realized that I was not getting the warning anymore. Maybe you have an intermittent ground problem somewhere in the trailer. Can you disconnect the Zamp while you drive? Good luck...
 
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