SMKN LS1

My 2016 3500 had this same problem. Service Trailer warning kept coming up while both towing and driving without a trailer. The dealer was no help as they blamed it on what they thought was corrosion in the 7 pin connector. The tech didn’t know that the contacts are brass and have a brass color lol. There was no corrosion. i did some research and narrowed the root cause to two possibilities: GMC Brake Controller Module 23337305 or Trailer Brake Controller 84108373 I replaced the module, located above the spare tire, and the warning disappeared. Took fifteen minutes to swap out. When I told the dealer service writer, they had no idea what a brake controller module was. Oh well. Hope it helps someone here.

I’d recommend reading the installation manual for a better source of information. My 2016 came with the OEM tailgate camera. The controller module (p 17 in the manual) only came with the IntelliHaul Towing Camera system and is not part of the original truck. Each camera comes with its own harness...none come with the original truck on the 2016. They’re pretty straightforward to install, especially the third brake light camera. I will say that the harnesses that run through the door jams for the two side mirrors were the hardest part, as they don’t quite fit in the oem boots. Echomaster suggested we call them for some tips and tricks if anyone else does this on their own. There’s a separate installation manual for the third brake light camera, but it follows the same approach as this one. It’s available on Echomaster’s website: An important recommendation is if you buy these kits, make sure it’s from a GM dealer or your warranty may be impossible to use. The 3 year warranty is great, but requires proof of purchase from said GM Dealer. I bought through eBay and luckily from a GM dealer that sent me an invoice with their name on it. This proved very useful when my passenger side door camera fogged up from moisture. Echomaster sent parts to my local dealer and upgraded both door cameras as this is a known issue and has been corrected for future buyers. I’m still quite happy with this purchase and appreciate the upgraded cameras.

So, I have installed both the GM CAMERA SYSTEM 19353504 and the separate OEM 3rd Brake Light Camera - 19355304 on my 2016 Sierra Denali DRW. Depending on how you set the dip switches on the controller, either you can default to the tailgate camera or the third brake light camera. On mine, I default to the tailgate camera because I don’t tow that often. To activate the brake light camera, I hold down the Back button on the oem radio display, enter into the camera menu, and choose the brake light camera. I might also need to have the transmission in Reverse for 7 seconds iirc. Hope that helps

Well, the dealer replaced the center cab light and it fixed the whistle. Look at the page before this one. Ultimately, GMC replaced my truck with a 2016 model due to the water leakage issue.

I did and it was a good decision for my situation. Can't speak for anyone else, but thanks for letting me know.

True. We bought a Tireminder TM66 tpms to add this feature to our '15 3500. The nice thing about this aftermarket system is that it covers both our dually and our travel trailer...factory systems can't do that!

Utmikeg - yes, I was referring to the optional roof lights. These came standard on our 3500 series. Our windshield was not touched during the repair. If it helps, our whistling noise was identical to the sound recorded on the video that a previous poster attached in this thread. If your noise sounds different, then the solution may be something else (i.e. windshield molding, on star antennae, mirror?) Good luck and I'll post here again if the noise returns.

utmikeg - which "enthusiast" are you referring to? In my case, the replacement center marker light on the roof seemed to cure it. My noise also came from the front windshield area. Having a passenger in the truck allowed me to isolate the location. My wife said it sounded like it came from the driver's side. I said it sounded like it came from the passenger side. So, it must be in the middle lol!

Dealer replaced my center roof marker light assembly for this issue. The tech used the "tape" approach to isolate the source. I'll keep an ear open to see if it's truly fixed.

I have this too, just discovered today. Driving southbound at 65 mph, the exact same whistling noise as in mwweiss's video. I have an appointment on Monday at the dealer for a soaked rear carpet and will mention if they discover what the cause of the noise is. early 2015 Sierra Denali 3500 DRW