Virgil Lee

Hey there Hunter Dale, and yes it can be very frustrating with the trailer tail light issue. I hope you have better luck with GM customer service than I did, they say that they want to help, but have a defined script they follow, and zero knowledge of what your problem really is. I'll bet that when you went to the dealer, they hooked it up to a Trailer Simulator and said it is working per design. HaHa, the design is flawed, the simulator only tests within the narrow current band that their system will recognize that a trailer is plugged in; there is an earlier GM TSB that actually has some steps to check and replace trailer light control module, before it got superceded by the latest revision to the TSB, which just uses simulator to simulate a trailer as a way to save money and not fix your truck. The dealer can go no further with any warranty fix, as long as it passes the trailer simulator test. FYI, my truck passed that simulator test three times, before it eventually failed the simulator test and they had to replace the Trailer Lighting Control Module, actually replaced it twice because the 1st one was also faulty. It was a nine month saga for me, with alot of frustration and calls, before eventually someone from the executive leadership team was assigned and assisted with getting the faulty module replaced. There is a relay in that module that will not pass power onto your tail lights, unless it senses a trailer is plugged in, the current band it needs to see on your trailer to turn on your tail lights is outside the range of many of the trailers on the market. In my case, I had 5 different trailers, counting the two boats and non of them had working tail lights when plugged into my 2020 3500 LTZ, all of them worked on my 2015 2500 LT. The 4 wire plug trailers worked fine on my wife's 2019 GMC Arcadia, yet GM "Customer Service" kept telling me that the truck wiring was fine and my trailers were not compatible with the new truck. Trips to the boat launch before the replacement, were more nerve wrecking with no tail lights before dawn. After the fix, the three 7 wire plug trailers work fine, I had to purchase a 7 wire to 4 wire adapter with extra resisters for the boat trailer tail lights to work. Did you know that the folks you call for GM customers service, including their supervisors are not GM employees, contract company is now used. I will give you $100, if you can find a phone number/contact for a GM Regional Customer Service Manager/VP that can help you. Best of Luck to You, I expected much better service and follow-up, from the GM that I was previously accustomed to. Now, my dilemma, is that they finally started the build on the Ford F-350, supercab, LWB, 4wd that I ordered, as I was not going keep the GM if the trailer lights couldn't get fixed, but I do like the Duramax/Allison drivetrain quite a bit, however, I believe the best way to let a company know you feel is with your wallet???

Hey Jordan, I am having similar problems with my 2020 3500 HD. Since I upgraded my 2015 2500 Silverado, I do not have any running or tail lights on 4 of the 5 trailers that I own. It seems the advanced trailer system used in the 2019 thru 2021, with integrated trailer towing was released before being fully vetted. I have purchased 3 of the 7 wire to 4 wire adaptors, including one from GM and all have the same results, the brake lights and turn signals work on the 4 wire flat trailers, but no daytime or running lights, which makes trip to the early morning boat launch unsafe and illegal. They have replaced the 4 wire plug on this new harness with 2 individual port plug-ins for all those folks out there, who need to plug in their front and rear cameras on their campers, again WTH? Thus far, all I can get from Chevy is that their trailer system is working fine and my 4 trailers are not compatible with their advanced trailer wiring system; can I please have my dumber system back, that actually worked?? WTH, the 4 trailers worked on my 2015 2500 Silverado and continue to work properly on my wife's 2019 GM SUV. It's ridiculous that GM has not addressed the problem and is blaming our trailers, I would expect more after the purchase of a $75k vehicle. Another annoying feature of the advanced system is a quick flash (pulse) of the trailer and truck rear lights about every 5 to 6 seconds when the lights are plugged into the truck and the truck is turned off. It appears that the advanced trailering system is looking for a resistive load that most the 4 wire trailers do not have. Note: to add further insult, my buddy was over with his 2021 Ram diesel and the lights work fine on his truck! Everyone having this problem, please contact GM, get a case number and do not accept their corndog excuses, don't they realize we vote with our dollars. I will trade my beloved Duramax for a Cummings or Powerstroke, if I can tow safely tow after dark!!

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?

I have a 2020 Silverado 3500 LTZ with the trailer towing package, non of my boat or landscape (4 flat wire connector pin) trailers will operate correctly. GM needs to get out a bulletin on this and let dealers know the problem. The turn signals and brake lights work, but the running lights will not work on any of these trailers. I used the same 7 pin to 4 wire pin adapter that I had with my 2015 2500 Silverado. I get warning messages that say the trailer is disconnecting while driving. I have replaced the adapter twice, with the same results. Additional, with the truck off and those trailers plugged in, I get both lights on the trailer flash on momentarily about every 5 seconds. I called the nearest dealer and they do not have a clue, they said to make an appointment, and leave the vehicle so a technician can troubleshoot it? I called a 2nd GM dealer in a more rural area, and he said that he had several customers with the same problem, and the adapters will not work with these new trucks, GM is trying to say that those trailers are not compatible with their harness. WTF? The problem is with the new technology, not the trailers that work with any other truck. The inteli-trailer and adding 2 camera ports instead of a 4 wire flat pin connector created this problem. Pease call your Customer service VP and let your voices be heard, It's ridiculous that after spending 70k plus on a truck that the trailer running lights do no work. The rural Chevy dealer, said they solved the problem, by connecting or splicing into the rear tail lights the old fashion way and connecting a new 4 wire pin.