No power to trailer lights

joekarter73 · February 21, 2021

Can't speak to anyone else's issue but mine (2021 Colorado with a trailer that just worked with my 2018 Silverado) ended up being a high impedance (cruddy connection) with the ground to the frame on the trailer. Not how I would have wired the trailer originally (I'm an ****** retentive electronics tech) but instead of running the ground to each of the lamps they bonded it to the frame near the tongue and then bonded each of the lights to the nearest frame section around the trailer. Cleaned up the first connector and viola everything works. My suspicion is that they designed the system to "look" for a certain level of return current and if it's not there the system shuts the power off to the plug. And now, since I have everything apart anyway, it's off to the part store for LED replacement lamps. Hope this helps'

JCRowe · May 13, 2021

I have a 2021 Z71 Suburban. Wanted to borrow a friends trailer and plugged it in. No lights. Works fine on his ford.

Put in my 7 pin tester no luck. Plugged in my 4 pin flat tester no luck. Could not tow the trailer without lights.

Took it to Chevrolet and they showed me their tester and that all was fine. They told me it is the trailer and asked me how old it was. At the end they told me to take my trailers to an RV place and they would redo my trailer so it will work. So the SMART system these engineers designed is not backward compatible on almost all trailers. So beware. Do not think you are going to rent a trailer that will work, borrow one from a friend or help out somebody in trouble. I am beyond upset with Chevy.

PS A lifter broke after 4000 miles on their most expensive and rugged suburban. It is a known defect. They replace all four on the right side, but would not replace the left side in spite of their being a bulletin to replace on the side if one breaks. So now I guess I wait to break down again in the middle of nowhere Utah and then wait 5 days to have it fixed.

I think I am going to build a trailer adapter with an inline resister on each lead to make a smart to dumb adaptor. Any suggestion of how many ohms?

Alas, what now. · May 13, 2021

Dang it. I was set to go out and buy a 2021 3500 Silverado after having problems with my Ford. Looks like I'd be going from the frying pan to the fire. I guess I'll research Dodge now and see what problems they have and then pick the one with the least amount of problems. I really liked that IFS on the Silverado one ton.

redwngr · May 14, 2021

Make sure the 7 pin plug isn't upside down.

I wouldn't have thought it was possible -- but, with at least with some trailer plugs, it is...

Edited May 14, 2021 by redwngr

Backyard Hack · June 6, 2021

I believe I stumbled on the solution. I had the same issue with my 2020 Sierra. I could hook my trailer to other vehicles and the lights worked. Hook it to my Sierra, and nothing. A seven pin tester indicated no power to the receptacle (although I could see very very faint flashing of some lights on the tester). I checked every fuse and all were good. Stumped, I looked at forums for ideas... nothing worked. Then my 5 year old daughter was "helping me" and inquired about the trailer hitch icon when I placed the truck in reverse - trying to be patient, I showed her how it magnified the hitch (I don't usually use this feature). When I put the truck in park, the park brake engaged and I suddenly had all my trailering lights. The display also inquired about which trailer was connected.

I'm thinking it is some sort of technical setting. Back to your trailer normally and before hooking the trailer and lights use the hitch magnification feature. Hook everything up, you should now have power to the trailering plug. Ever since I started using the magnification feature, I have power to the receptacle. If I forget to use the magnification feature the lights don't work on some of my trailers, but do on others??? Simply use the magnification feature and the lights work on every trailer... go figure???!!!

Fesilva · June 10, 2021

On 5/12/2021 at 9:00 PM, JCRowe said:

I have a 2021 Z71 Suburban. Wanted to borrow a friends trailer and plugged it in. No lights. Works fine on his ford.

Put in my 7 pin tester no luck. Plugged in my 4 pin flat tester no luck. Could not tow the trailer without lights.

Took it to Chevrolet and they showed me their tester and that all was fine. They told me it is the trailer and asked me how old it was. At the end they told me to take my trailers to an RV place and they would redo my trailer so it will work. So the SMART system these engineers designed is not backward compatible on almost all trailers. So beware. Do not think you are going to rent a trailer that will work, borrow one from a friend or help out somebody in trouble. I am beyond upset with Chevy.

PS A lifter broke after 4000 miles on their most expensive and rugged suburban. It is a known defect. They replace all four on the right side, but would not replace the left side in spite of their being a bulletin to replace on the side if one breaks. So now I guess I wait to break down again in the middle of nowhere Utah and then wait 5 days to have it fixed.

I think I am going to build a trailer adapter with an inline resister on each lead to make a smart to dumb adaptor. Any suggestion of how many ohms?

I had this problem driving me crazy for two weeks smh mine ended up being fuse 74 under the hood 30amp. 2019 GMC 1500 Denali

Fesilva · June 10, 2021

4 minutes ago, Fesilva said:

I had this problem driving me crazy for two weeks smh mine ended up being fuse 74 under the hood 30amp. 2019 GMC 1500 Denali

dan nolan · July 25, 2021

On 5/23/2019 at 1:24 PM, P Bolton said:

Ok I hooked up a trailer to my 1 month old 2019 Chevy Silverado today for the first time and had no trailer lights. Hooked up my second trailer and also had no trailer lights. Connected both trailers to my father-in-laws truck and both worked fine. Checked both sockets the flat 4-pin and round 7-pin and had no power at either one. Anyone else had this problem?

Yes im having the same problem take a tester to the plug nothing every time I hook a new trailer to my truck its a problem why

Shawng · August 7, 2021

My truck works perfect with my job trailer that’s all LED and won’t work at all with my body trailer. Just spent a week redoing the boat and it still doesn’t work. Never considered it being the brand new truck and thought I ruled that out by using my other trailer all the time.

Tim Lee · August 14, 2021

I have a 2021 1500 LT with issues too. No lights work at all when I plug in the 7-pin. When I turn headlights on all the running lights work, but no signals or brake lights. Any ideas?

SandraStacks · August 14, 2021

try to change it

Virgil Lee · October 13, 2021

I have the same problem with 4 out of 5 trailers that I own, no running or tail lights on any of them when connected to my 2020 3500 HD; all the trailers worked fine on my 2015 2500 HD that I traded in and also still work on my wife's 2019 GMC SUV. I am several weeks into the Chevy senior Advisor trying to get me an answer. When is GM going to acknowledge there is a design flaw that needs to be corrected, it can't be that 90% of the trailers being used are incompatible with the advanced trailering system, designed by GM?

Pete Sgro · April 27, 2022

Did anyone ever find a solution to this problem? I am having the same problem on my 2021 Silverado 1500.

gemarsh · April 28, 2022

Have a 22 3500. I have 4 trailers with brakes, a '90 Titan that has had led bulbs installed, a '09 ADS seed tender w/ incandescent, '21 and a '22 H&H with leds.

No problem with any light issues, but issuse recalling the brake gain after shutting down the truck and restarting. Something like Error, can not recall brake gain. Check brake gain. It's always correct as to the adjustment, that I have set for that particular trailer.

DIC came up once with Check Trailer Right Turn Signal Lamp. Had a bad bulb. I like the system so far.

I also dislike not being able to choose the correct trailer while in gear or moving. It defaults to guest trailer.

Pete Sgro · April 29, 2022

You are having luck than me. I have hooked up six different trailers and have problems with everyone. It goes from everything fine to no trailer connected to check a specific light to trailer connected in many different sequences. Dealer has no clue because it is hard to diagnose an intermittent problem. I think this falls on GM to give them some guidance.