The front grille is a polycarbonate shell covered with a
thick layer of polyurethane (the standard PPF material). I haven't seen any technical information on how thick, but certainly much thicker than commercial PPF (which is generally 8-12 mils: 1 mil = .001"). So adding a dozen-ish mils to the original polyurethane
likely won't affect the function of the radar behind it - which as far as I know is the only type of sensor behind the grille. Polyurethane is used in aircraft radomes because it's transparent to radar. Others have reported no issues covering the grille with PPF. That said, the
sonic sensors are sensitive to even dust or insects covering them sometimes, and I have no idea what else - if anything - BMW stashes behind the beaver teeth. BMW thought they were important enough to add a heating element to melt snow and ice (which said element may ultimately affect the adhesion of the PPF - unknown). PPF is easily removable, so if you get continual error messages you can just strip it off, realizing that you
have altered the original engineering design, which most of us have already done to our cars in one way or another, probably more significantly than adding PPF to the grille.
