2014 Silverado LT headlights and taillights not working

[95_togo]

Here’s a weird one for you…. I have a think diagnostic tool for my phone and can activate each headlight individually through the app by connecting to the BCM…. But there doesn’t seem to be a diagnostic for taillights.  High beams work, turn signals in both front and back work, everything else in the truck works….. except DRL, headlights and taillights…. My research points me in the direction of the switch…. Is this a correct assessment? Or am I jumping the gun on this one? 
Any and all advice appreciated! 

Edited December 30, 2024 by 95_togo
More info in title

[Lovin'theSouth]

Isn't there a dash light, indicating when the headlights are on? Checking the state of that light may help narrow it down. If you switch on, and the dash light activates, it's not the switch, right?

[BO TIE 1]

Check the fuse in the underhood fuse box. Drl has it's own fuse. 

[95_togo]

On 12/30/2024 at 1:49 PM, Lovin'theSouth said:

Isn't there a dash light, indicating when the headlights are on? Checking the state of that light may help narrow it down. If you switch on, and the dash light activates, it's not the switch, right?

You’re right it’s not the switch, when I change switch positions, an indicator warning on the DIC says auto lights on or off.  I read in another post that it could be trailer wiring, since it seems to coincide with a trailer hookup a few nights ago, I’m leaning towards this now, but have checked all the trailer fuses under the hood, there was a 20A burnt out so I replaced it but the problem persists.  Any ideas where i I should look next

[95_togo]

Well… I’m an idiot.  Apparently that 20Ai replaced a few days ago was the problem, didn’t realize that the DRL wouldn’t come on until it was in D! The headlights work with the switch so I’m all fixed up.  Thanks for the input all, it’i appreciate you taking the time to reply!