I was curious about the ACC sensor, cover and mount so I popped the cover off of mine and it is just snapped on with tabs around the edges. You can also reach in from the edges with the cover in place and feel/push on the sensor. My sensor feels solid with no movement. Here are a few pictures with the cover off. One thing I found interesting, it appears that they just use a hot knife to cut some pieces out of a standard grill to make room for the sensor/cover, you can see the melted edges and the bottom cutout isn't even straight.
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