Don't know whole lot about modern cars, here's what I do on my
classics. Determine if water is coming in under use, or when sitting.
Blast car with hose, keep hood closed, spray around windshield top
first, than side post, no leaks, than blast top of cowl. No leaks, than
suspect heater box, open hood and blast heater box. No leaks, than jack
car up, and blast wheel opening.
By confining tests to specific areas, problem should reveal itself.
If all else fails, use dish detergent and soap everything up, than
gently moisten with hose set for soft spray. Now take an air hose, and
blast from inside, trouble area will foam like a mad dog.