What year is your truck? 13?
Correct me if Im wrong, but I didn't think the PCS system on the 13-15s had anything to do with the radar sensor. I thought it worked by sensing panic stops, basically the time between throttle input and brake input. If you move your foot from throttle to gas pedal in less than some amount of time, that's a panic stop and it kicks in PCS and just applies full brake pressure and seatbelts.
And since you can disable radar cruise on the stalk, a new grill shouldn't affect either one of these systems. Unless I'm wrong about how the older PCS system works of course.