Work truck 7way plug

So I have a 2nd gen (2012 rock warrior) and I was pulling a car trailer, doing the norm to make some chedder. I got to my destination and realized I have no running lights. At this point I realize it's starting to get dark and I gotta head back, gonna take me about an hour or so. Next morning I grab the old 7 way tester and sure enough no running lights. I start the normal process and start checking fuses. Found the 30amp fuse for the running lights under the hood was blown, it got replaced. A couple days latter I am pulling my boy scout troops trailer and guess what, no freaking running lights when we pull into camp. So next morning I check fuses again, nothing is blown. I think to myself well there might be other fuses pertaining to the trailer lights so I get out the ol manual and sure enough there are some under the dash. Now I am a 300lbs over six foot man, getting upsidedown in the driver seat isn't easy but I do it and start checking them pesky little buggers. Again nothing blown. Well crap. At this point I wait till the end of the campout, go home, and proceed to check the plug with my multimeter. I definitely do not have running lights. Do a continuity check on all the wires for the seven way. They are good but the truck side of the wiring has no running lights. At this point I realize I don't want to exterminate electrical Gremlins myself so guess it's time to call the shop. So as of yet it has been 2 days, my truck has been at the dealership garage and they still have no clue why I have no running lights. My brain, aka the wife, tells me the Toyota dealerships know best and I should just trust them to get it done. However I used to work at a Chevy dealership and know that sometimes the dealership techs are just as dumbfounded as we all can get. So I am searching the forum to see if anyone else has had this issue, no running lights on four pin and seven way with no blown fuses or apparently burned or shorted wires. Any response is respected and viewed.

 

Truck running lights work correctly when not towing?

Then once you plug into a trailer you lose all running lights on truck? That right? When you’re saying running lights, can you be more specific as to what doesn’t work?

 

No just running lights on the 7 way and the 4 pin.

 

Ok so update. I finally got the truck back from the dealership. They had to make a call to their master field tech and have him come in and look at it. Apparently all it was, was the sealant the factory uses to weather proof the plug on the harness (truck side) had some how not beed completely applied. So he pulled the connector off the wiring cleaned it andareaplied a silicon sealant, I woul of just cut and spliced a new one. Anyway all fixed now. Who would of thought to check the sealant in the connector? Guess that's why he is the Master Tech.