Silverado trailer plug troubleshoot

I have a 2007 (new body style) 2500HD and having issues with my taillights. With no trailer hooked up I used a meter on the plug checking ground continuity. I have ground for my white wire (which is ground) but also showing ground continuity for my backup and taillight wires on the plug. If I pull those 2 specific fuses there is no longer a ground continuity with them. Checked at the fuse block under the hood and both of those fuse slots (with fuse removed) give me ground continuity. Any ideas why I am getting this?

Did this just happen out of no where, or have you just replaced some lights etc??
What pin connector do you have (flat 4, round7 etc)??

I have had the truck for several years. Been an issue from day one. Just finally pulling more trailers so figure I’d better address it.
Always when I pull my bigger trailers the “check trailer wiring” light is on on my dash. I did replace the relay? or whatever it is called under the bed above the spare tires. That helped get my trailer brakes working. Standard factory 7 round plug.

I think the trailer wires are now separate from your vehicles regular turn and brake lights now. This prevents problems with your vehicle lights if the trailer is wired incorrectly.

Find what module separates the signal from your vehicle lights and the wires going to the trailer. There is probably some problem in there, or a separate fuse for trailer power.

Yes, the truck taillights work fine. So maybe there is a module somewhere before the fuse block under the hood?

Without being able to see your vehicle in person, not sure how it is wired… How is the trailer wiring wired to the truck?? Hard wired or with a plug??
I would make sure you don’t have any wires that are rubbing on the chassis/frame causing the issue(s)… Are the fuses you are pulling blown?? and do all the truck lights all work correctly??

So it seems as if my bigger trailer lights work fine. Smaller trailer lights are wishy-washy. Gonna install new led lights on the little trailer. Still have that “check trailer wiring” light coming on on the dash when I am hooked up to the bigger trailers. Could it have something to do with trailer brakes? I did replace the trailer brake relay located above the spare tire. But that did not solve that problem. Fuses are not blown.

The trailer wiring is located on the trailer.

I’ve seen LED lights cause all kinds of trailer light problems.

Poor quality LED lights don’t show enough electrical resistance to make the computer system think that lights are hooked up, even though the lights do work.

Same reason cars converted to LED bulbs for turn signals hyper flash