What puzzles me about all this is why the investigators did not compel the companies to produce the exact mechanisms by which they cheated emissions as part of

What puzzles me about all this is why the investigators did not compel the companies to produce the exact mechanisms by which they cheated emissions as part of the settlements. I guess it doesn't really matter, since what you're chiefly interested in is the manufacturer ceasing the behavior and not repeating the offense, so that might be why they didn't.