Flar towing

[Glenn Dausch1]

Bought a 2025 GMC Sierra 3500 4x4 Denali to tow behind our motorhome. Was assured is was not a problem and even was showed protocol in owners manual.  Went with the Demco Air Force one braking system since MH I designed to supply air to tow vehicle thus avoiding any electrical connections.  Went with Etrailer plug and play wiring harness that connects into the tail lights.  Also went with the Etrailer system that charged the batteries as well. When I go through the protocol of getting ready to tow and the electrical connections is made I have all the lights in the rear of the truck.  The issue is when you put the truck in park the steering wheel locks up, obviously you cannot tow like this.  What I did next is disconnect the charging line to the battery, this makes the towed vehicle protocol go perfect and I can tow the vehicle.  The problem now is I have no lights on the rear of the vehicle. I think the problem is the module in the LED taillights, that need a signal rather then a 12 volt source. All the plug and play wiring from Etrailer have diodes in them. I have been getting nothing but the run around from the GMC dealer. Have called GMC help line and relayed exactly as above but not even a response.  Ran into another person towing a 2500 and had the same problem, and the same response from GMC.  He ended up putting magnetic lights on which look absolutely terrible.  Any suggestions out there.  As far as I am concerned I have a $90,000 vehicle which does not conform to federal standards.  Is that a reasonable assumption 

[Jsdirt]

Nothing I say is really going to help you feel any better here, but GM, as far as I'm concerned, is DEAD.

 

Based on past experience turning wrenches professionally for 14 years, owning a GM product for 16 painful years, and reading story, after story, after ENDLESS story of problems, I'd seriously recommend dumping that vehicle for ANYTHING else. Preferably something built when manufacturers still SORT OF gave a crap about their customers - at least something built before the 2007 model year. Your wallet and your sanity will thank me later.

 

And if that truck has the 6.2, you had better check up on that engine recall before the thing blows up on your next trip. 

Edited May 26, 2025 by Jsdirt

[64BAwagon]

Sounds like the stuff from E-trailer doesnt integrate with the truck. Not sure how that is GM's fault. The fact that it doesnt integrate with the upfitter items you tried to add isnt an indication IMHO of it not meeting any standards. The new trucks are very sophisticated electronically and ant changes to them can have far reaching implications. I would research as much as possible on RV forums for others with similar issues and see if they had solutions. It very possible that you will need to use additional lights other than the OEM ones on the truck. There are few, if any dealer level people that have the training and talent to troubleshoot issues like this. GM has little to no tolerance for people modifying the vehicles other than qualified upfitting companies. Just because a dealer made a claim that something would work for a particular purpose does not mean it actually will. Dealers are notorious for wild claims. 

[Jsdirt]

NOTHING should be this frigging complicated in making an attempt to do what it was designed to do, especially on a $90,000 truck.

 

What the hell good is a truck if you can't even tow with it because the G / D electronics won't let you? RIDICULOUS!