I'm a tech myself but I'm looking for additional TSB or other input on a specific DTC issue, namely P2201 / 2214 on a R172 M276 (40 k miles). I understand the code, what it means, what may be needed to correct the fault etc. etc. but I suspect that there is a BIG back story on this. Cancel the code and all is OK for a while and then bingo back it comes. It appears that MB have been changing NOx sensor Pt No.s multiple times and that there is a "design" issue rather than a problem with the sensor. In short the NOx storage cat (NAC) needs to be regenerated signalled by the MIL / ECL illuminating. This engine is Stratified Charge Petrol with NAC rather than the current design full Ad Blue SCR cat. I've picked up that MB are keeping their cards tight to their chest and info on this is not being published via TSB, but by other more "secure" channels. Any info would be much appreciated should there be any helpful MB tech staff out there.