CLK2002 / cp3377:
I have a late 2014 (Nov) CLS 350 Shooting Brake. I have been having NOx sensor problems since I suspect the Diesel Software Update was applied to the car in late 2020. I like to do most maintenance myself, as I have good workshop facilities and the time to do it now (semi-retired), albeit that some of my software is now a bit dated. Rather than just accept on face value what Mercedes, their main dealers and a lot of independents recommend or do to solve NOx related errors, I have spent a lot of time hands-on and researching the problems in a lot of detail. Part of that research has been discussing this on another MB forum, which has provided a much better understanding of the problems. Internet search 'NOx Value 751' should take you to it if you are interested - a bit long-winded and repeated in places, but there is a lot of interesting detail and input from a couple of guys who really do seem to know their 'stuff'. This has provided me with a much better understanding of the problems, but I still have not bottomed things out fully in my mind yet, and need to find people who also have W218 models and are prepared to share details of the software and hardware mods that have been applied to their vehicles.
From my investigations, I believe that most of the NOx sensor changes that have and are still being done because of errors caused by the Diesel Software Update are 'doomed' to fail because they are mostly short-term 'bodges' and the only true long(ish)-term fix is to have the 'retrofit of Special Equipment code 30o' applied (search on that - it was mentioned on this site before, but its significance seemed to be ignored). The facilities to do this retrofit appear only to be available at the main Mercedes dealers, or the independents who have spent the money to have full access to the on-line Mercedes Xentry etc. Mercedes do not appear to be openly admitting this or publicising the retrofit, possibly because they will be inundated with claims - perhaps that needs to happen(?). I might be wrong, but why is this retrofit there, hiding under the radar and only accessible through 'official' channels? If the main dealers are fully aware of this fix they don't seem to be being very honest with the owners(?).
What I am currently interested in are some details from circa. 2014 W218 350 BlueTec (642 Engine and 725001 Gearbox) models that have had the Diesel Software Update and if the 'retrofit of Special Equipment code 30o' has been applied as well, then all the better:
Specifically, the details of software updates on the:
N3/9 - Motor electronics 'CD161' for combustion engine 'OM642' (CDI);
Y3/8nd - Transmission control for 9-speed transmission (VGS); and,
N118/5 - Selective catalytic reduction (SCR 02) control units.
I believe, and have seen proof, that all of these (at least) get updates as part of the Diesel Software Update, and then again for the 'retrofit of Special Equipment code 30o'.These can be obtained from a Xentry quick test and/or a copy of the full datacard detail.
Specifically, the details of option codes fitted to a vehicle that has had the 'retrofit of Special Equipment code 30o' applied, and then the new part numbers for the NOx sensors (they will be different from the original ones).
The code information can be obtained from a VIN decode (readily available for free on the internet - and, correct if they are accessing up-to-date datacard information ) and from any main dealer or independent who have access to the on-line datacard. The correct sensor numbers will be available from a main dealer or independent who have access to the on-line datacard and/or Electronic Parts Catalogue (EPC).
I would also like to find out the full range of NOx sensor part numbers that have been applied to all W218 models during their life so far and all the modification codes that were applied to make the sensor number changes necessary.
I believe to get that information it is necessary for someone with access to the on-line Mercedes' EPC to search for the parts on a generic W218 (saloon or shooting brake) (i.e. don't enter the full vehicle VIN, only the first six numbers). I have made enquires about this, but can understand if none of the independents want to stick their heads too high above the parapet for fear of Mercedes' wrath.
So:
Best Regards:
Edward