Hello, interesting article and responses & helpful, thanks. I have a,question.....If the build up of soot is so great, would it not show up in an emissions check? Had P0405 code for a while (yeti 4x4 170 ps).. Sprayed EGR cleaning fluid in and I've used an additive (millers), every third tank for 10 years. Engine management light resets & remains off, until the 3 Rd restart when it illuminates again..... Same procedure every time....TUV passed last week and emissions fine and no mention of EM light. Acceleration, top speed & fuel economy all good, especially fuel economy, autobahn, rural and a little town use and achieving about 1000km on full tank. manifested itself after using a power wash......water in to the engine bay and electrical fault? I've checked sensor and it's o and wiring seems ok. Any thoughts?