That's basically what the tune does, but it doesn't have to, at least all of them; just those that result in limp mode or no operation technically. Many people are surprised BMW made diesels and more surprised an SUV like the X5 was offered with one. I think the requirements are stupid, but that's mostly because the systems are entirely unreliably and expensive to repair -although aftermarket NOx sensors, DPFs and SCRs are finally becoming available for some vehicles - and generally totally and poorly understood and economically repaired by the so-called dealer technicians. That, and there's were other emissions control methods that are as effective and more reliable, but that reduces profit margin, inflates the price which reduces diesel sales, and removed an absolutely considered source of profit over the lofetime of a vehicle.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim