Since I bought my 2015 Tahoe LTZ, its been raining on me inside my truck everytime we get heavy rain or alot of snow. NICE....... The dealership who seems to be always wrong, had me replace the antenna and the seal for the sunroof......did not change a thing almost $1000 later.
I noticed that my seals above my windshield on each side of the arms that hold the windshield are different.....The passenger side which is not a problem is flush/flat.......The driver side (the one that leaks) is puckered.....not flat..... Attaching pics for reference...if anyone knows of an easy fix or what I need to do to fix this any help would be appreciated......

Driver Side - Side that leaks, its not aligned correctly and the seal is puckered.

Passenger side - perfectly aligned and seal is flat

 

If you are not the original owner i would check on the windshield that the windshield is OEM. It looks like it isn't, since I'm not sure it's even possible for the factory to put it on that out of line. You can try some urethane seam sealer 3M makes if you want to go the cheapest that MIGHT fix it. May be better off getting the windshield replaced. Just idea from someone that spent a year trying to stop a leak that ended up being a replaced windshield that never had enough adhesive in the first place. Also don't recommend going through an automatic car wash not that you have but like to shoot that pressurized water right at your windshield seams so they can affect it over time.

 

The tale of 2 car companies . I own a GM Chevrolet Tahoe . Tahoe equipped with GPS/Navigation, Satellite radio and OnStar. Uses a "shark-fin" antenna to receive necessary signals. Built with part 84346801 and since replaced with part 84081915 for obvious reasons. GM determined that a drain hole on the uphill side of this antenna would cause it to fill with water and eventually fail. Our Nav system began failing intermittently just before warranty and died completely shortly after. I had to replace the antenna with the new one - drain hole now on the bottom - myself. GM offered no assistance but did indicate some cars are illegible for a repair per service bulletin but not mine

Subaru 2017. AC failed after warranty. Condenser leaking. Replaced at my expense. Subaru later determined it may be defective in some cars. Reimbursed me completely for repair and examined the replacement to ensure it was not subject to the same failure.

 

Take a hose and run water straight out of the hose in various areas and look for the leak inside. The typical location is from the drains for the sunroof. They come unhooked easily. If you just hook them back up, they'll come off again. I zip tie them to the tubes and never have problems after that. You need to drop the headliner a little to get to the drain tubes.

You can also open the sunroom and pour water in the drain area and see if that triggers the leak. If so, you have a crack in the drain pan or the drain line is disconnected.