The models affected by this do not use DEF[1] I used to understand the system fully but have lost some of that as it's no longer important to me. In short, the

The models affected by this do not use DEF[1] I used to understand the system fully but have lost some of that as it's no longer important to me. In short, the CBEA engine line has a complex emissions control system consisting of 3 separate catalytic converters that each must be regenerated from time to time, and two exhaust gas recirculation systems. These regeneration cycles reduce performance and increase fuel consumption. For example, a DPF regeneration cycle closes a valve in the exhaust which increases system pressure and thus system temperature, while also triggering a post-combustion fuel injection -- injects unburned fuel into the cylinder on the exhaust storke -- to increase the exhaust temperature to burn off soot that accumulates in the particulate filter. It is likely a change in the schedule of these regeneration events that is necessary to bring the vehicle into compliance. There is a long PDF[2] that goes into detail how the emissions systems work on these cars. [1] http://www.myturbodiesel.com/images/dpf3.jpg http://www.myturbodiesel.com/images/dpf3.jpg [2] http://www.natef.org/natef/media/natefmedia/vw%20files/2-0-tdi-ssp.pdf http://www.natef.org/natef/media/natefmedia/vw%20files/2-0-t...