tldr; Asking out of absolutely curiosity of what the remote auxiliary radiator is for as I can't help myself but to know how things work.

Upon obtaining my new-to-me 2019 CMS All4 Auto, I did some research of what preventative maintenance/mods I can throw at the car and coming across a few articles of owners losing coolant because of rock banging up their auxiliary bumper radiator, I have a rock guard on the way (this thing) to prevent that issue. Upon realizing this little additional coolant radiator exists, I am wondering what it's for. As far as my observations go, only the automatic models have this radiator. I know most automatics these days are cooled by a tiny little popcan sized coolant/ATF heat exchanger core mounted to the transmission that circulates engine coolant through it to extract excess heat from the transmission. What I am curious of, is this remote radiator an extension of the existing radiator coolant loop simply for additional coolant heat extraction simply because the transmission tips it over the edge? Or, is there a separate coolant loop or solenoids that turn on/off this auxiliary radiator? It looks the LCI bumper has a totally different vent shape, did they get rid of this remote radiator on the LCI refresh?

 

I can't answer your technical questions, but after reading several reports of punctures of that aux radiator, I put that screen you posted on my 2019 JCW. BUT you'll find it's only plastic. Not sure how effective it would be on a big rock. So, I rolled up a small piece of plastic "gutter-guard" into a cylinder-shape, and zip-tied it in place between the radiator and the front bumper on my 2020 JCW. It will slow down a decent-sized rock, I'm sure. I've used "gutter-guard" in some variations of this on all my cars for at least the past decade. I've caught some interesting debris that would have otherwise struck the radiators, and a couple of times had to replace the home-made screen device after something hit hard enough to break through the first layer or break a zip-tie that holds it in place. Definitely agree a bit of extra protection here is prudent.