No power to trailer lights

[Roger Humphries]

I have a 2020 Chevrolet 2500HD, my tail lights & side marker light doesn't work. But everything else works R&L turn signals, brakes lights & brake all work. I have no power on #4 on either plug. The one in the bed is the same as the bumper, no power on #4 tail lights & markers. The is fuse (#41) is good, also put anew in still nothing. Any suggestions?

 

 

[davester]

wiring or connector at the back has some problem?

[PBrown1]

Wiring is NOT the problem. You need to take it to the Chevy Dealer and get an update to the Trailer Lighting controller. I had this issue. 12V was not present on the running lights for the trailer. Stop lights and turn signals did work however. I have a 2020 1500 Siverado and they had to swap the controller. Here is the bulletin.

NHTSA Bulletin 20-NA-198

https://static.nhtsa.gov/odi/tsbs/2020/MC-10181721-9999.pdf 

2019 Model Year vehicles, equipped with U1D, use the K68 Trailer Lighting Control Module to control all trailer lighting through pulse width modulated (PWM) voltage. The Trailer Lamp Control Module has a current handling capability on the running lamp circuit of about 9 amps. On a trailer with a large number of incandescent lights, in-rush current can exceed 20 amps before it settles back to around 8-9 amps. During this inrush or "marriage" current period, the Trailer Lamp Control Module sees the current as an "overload" and goes into protection mode. 

 

[Dragon rider]

On 11/23/2019 at 7:48 AM, Rsktm300xcw said:

Has anyone with these problems tried the trailer light module reprogram I mentioned earlier. It helped my truck a lot. I believe that it widens the acceptable amp draw of the trailer lights substantially. My running lights were drawing too much so it would shut down so I swapped all trailer lights to led. Then my brake a d signal lights were not drawing enough so it shut down so I added the resistors. Now after reprogram and new lights everything works as it should. Also eliminated the trailer disconnected message that used to show up frequently. A combination of new lights with the proper amperage draw plus the refresh has almost completely eliminated these problems.

Where did you put the resistors? Im trying to fix my 2022 now. Lights all work durring the day when the running lights are off. As soon as I turn on my trucks headlights (making the running lights come one) the turn signals stop working immediatly, so it's deffinitly a power delivery issue... What does the dealer reprogram and where do I put the resestors?

[Happytown]

This thread was very helpful, wanted to contribute something back:

 

Spoiler:  replaced Fuse 74 TIM, fixed our issues. 
 

 

2019 Sierra SLT X31 Texas Edition, just bought it used about a week ago.  First time towing our small utility trailer, had trailer lights when we left home Friday.  Two days later (today), no trailer lights at all.  Even with no trailer connected, the monitoring system was showing trailer connected, and flagging an issue with Left and Right turn lights.  Also at this time, the truck turn signals were "fast blinking" like an old school flasher going bad.  We left the trailer at the camp and got on the road. This is when we also noticed the Fuel "distance to empty" was not updating, just frozen at like 283 miles even after driving 20 miles or so.  Long story long, I head read this entire thread by the time we hit the Dairy Queen (I'm riding shotgun, its my sons truck) and I hopped out and pulled Fuse #74, sure nuff, busted.  Replaced it with a spare and all symptoms resolved with the trailer monitoring system and fuel DTE updated immediately. Hope this helps someone else. 

[Figster84]

I have same issue with a 2020 Silverado 2500 HD. Really sucks can’t tow anything till issue is fixed all fuses are good Chevy should address this issue.

[Allan Williams]

On 6/6/2021 at 12:59 PM, Backyard Hack said:

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???!!!

 

[Allan Williams]

tried the magnified hitch trick and it worked but sadly only once. can't seem to replicate what I did. This is my 5th suburban and likely my last GM product

[GMCustomerService]

On 3/3/2025 at 2:58 PM, Allan Williams said:

tried the magnified hitch trick and it worked but sadly only once. can't seem to replicate what I did. This is my 5th suburban and likely my last GM product

We want you to love your Suburban again, Allan. We want to learn more, and ask that you email us at [email protected]. Please share your full VIN, some further details regarding your concerns, and the name of your preferred dealership. By sending us a message, you consent to the information you provide being monitored and recorded by GM or those acting on GM’s behalf, subject to the GM Privacy Statement: https://www.gm.com/privacy-statement.