[inversionOf]

Both of those platforms use Urea systems, as do larger and more expensive VW/Audio vehicles. The issue is purely in the small, inexpensive vehicles.

The NOx problems were mostly resolved through the injection of urea into exhaust gases (e.g. AdBlue), dramatically reducing NOx emissions while leaving the efficiency and power unaffected. Urea systems add an extra cost and complexity to the vehicle though (not to mention that you need to top up your urea additive occasionally), and VW seemed to find a loophole that allowed them to make small, inexpensive cars without urea injection. They did this by injecting fuel into the exhaust in the absence of Urea, but to achieve the same effect. But this can gunk up the NOx trap if used endlessly (it is far less precise than urea, obviously), reduces fuel economy, etc, so they built this One Little Trick that only actually does that during identified tests.

[binarycrusader]

I don't understand this assertion. The two VW diesel (US) automobiles I've owned have had an AdBlue system. One was a base model Jetta TDI and the other a Passat TDI (which I now want rid of).

[inversionOf]

And the vehicles in question -- the ones that are causing VW these issues -- do not have any urea injection system. That's the whole point.

http://ask.cars.com/2012/11/why-do-some-volkswagen-diesels-u...

VW claimed to have a trick that removed the need for it on their smaller, lighter cars. But that trick was a trick that only allowed them to pass EPA tests.

[binarycrusader]

Ah, so come to find out, the Jetta TDI 2009-2014 did not have AdBlue (I mistakenly believed the one I owned previously did, a 2010 model).

However, VW added the AdBlue system to the 2015 Jetta TDI -- perhaps because they knew that this was a problem:

http://www.bimmerfest.com/forums/showthread.php?t=765593

On top of that, even though the Passat has an AdBlue urea system, it's still affected:

  On the open road, a Volkswagen Jetta TDI blew through the
  U.S. nitrogen oxide (NOx) emissions limit by 15 to 35
  times. A VW Passat TDI (with urea aftertreatment) was 5
  to 20 times the maximum.

http://www.greencarreports.com/news/1100125_vw-diesel-emissi...

So yeah, I'm not a happy owner right now.

[switch007]

Not sure if there are USA/Europe differences with BMW's urea system (likely), but Blue Performance (urea system) is not standard on all BMW diesels in the UK (in 2014 anyway).