My car (Fritz) has recently had the diesel emissions TSB performed. Since then, DTC P20EE (Cat below threshold) has occurred 3 times. First the dealer replaced the (I believe) NoX sensor. Second, they said they repaired an exhaust air leak. Lastly they found the passageway in the exhaust restricted with hard, tan ash where the DEF spray nozzle mounts. The opening to the exhaust shrunk to about 11mm or 7/16 inch. They cleaned the ash from the pipe. This may very well fix Fritz. After talking it over with a couple other techs I worked with during my career at MB and Nissan as a technician for 42 years, we have concluded the ash is a result of the use of incorrect engine oil used in my car before I bought it, used.
At the time of the TSB being performed, I had the MB dealer change the oil and filter. Let's hope they really did instil spec 229.51 or 229.52. Hope this is the end of Fritz on the fitz.

 

Consider a full DPF/EGR/SCR delete. It'll make the car (and you) happier.

 

Thank You. I surely will after the extended warranty from the emissions TSB runs out.

 

What's TSB?
Those cars are subject to AEM. (Approved Emissions Modifications) and having warranty, you don't need forum help. Did you collect the check?
https://www.epa.gov/enforcement/daim...vil-settlement
I deleted DPF on 1 of my Bletecs and now am converting it back.
The delete was forced over 3 years ago by MB USA not being able to supply new DPF. Now new DPF can be bought aftermarket for less than $1000.
The sedan with DPF delete delivers lower mpg, than the one with DPF working although the small difference can be due to different driving style (freeways v/s more city driving)
DPF delete still passes NV smog test, what is sniffer on the rolls.

 

The AEM is a TSB/technical service bulletin. I'm not requesting help, merely offering a bit of insight as to what could contribute to the DTC P20EE/cat below threshold.

 

I don't think you can wrench bulletin. It is wording, but misleading.
My 2014 had almost all exhaust replaced under AEM and Nox sensor as well.
So reading your post I understand that the new parts developed defects or poor installation?

 

My car has been back to the dealer 3 more time since my last post. Same code, P20EE. They have quit giving me paperwork on recent visits, although I have signed for work authorization each time. The light stays out for 2 or 3 weeks after each time they have had it and done what, I don't know, although each time they extinguished the light. The light is on now and my car goes in tomorrow. I asked the service riter if he would contact Mercedes, to have a specialist look at my car. The service writer said, they won't send a specialist for that. Tomorrow I'll insist on documents from all recent visits. when/if the code comes back, I'll contact Mercedes and ask for them to get proactive.

 

My car got a new EGT temp sensor on Wednesday, 8-23. On Saturday, 8-29 MIL on again. DTC for EGT sensor, Bank 1, sensor 3. Goes back to dealer tomorrow.

 

Just got home from dealer. Service advisor informs me that my car only has 2 EGT sensors. They are ordering another rear EGT sensor, same one as they replaced last Wednesday.

 

September 6, Benz got new EGT sensor at dealer. Dealer erased code. Yesterday, Oct 9, MIL back on. DTC for rear NOX sensor and cat efficiency insufficient. Dealer ordered new Nox sensor, again. This morning I talked with Mercedes Benz USA, they are now aware of my car's recurring issues. Hopefully they will become involved.

 

Sounds like they need to find the root cause to get this fixed. Good luck.

 

Quint22 I certainly hope so. Factory secret agent techs have confidential intel.
I worked as a new car dealer tech for 42 years. Mercedes first, then Chrysler, lastly Nissan. I had to go to where the repair dollars were. Back in the 80's Mercedes just didn't have enough repair opportunities. On to Chrysler, It had to have been the winter of 88-89 or 89-90, I traveled to a tech class regarding Chrysler's A604 auto trans.
The A604 had a terrible problem with bump stop. At a red light it felt like the car behind you, bumped into you. This class addressed that problem. The clearance in the low/reverse clutch became excessive after low milage. The TCM couldn't control release and apply smoothly with too loose clutch packs. No TSB or anything in print ever revealed the fix. We were instructed to stack the L/R clutch way tighter than specs. The gave the TCM very good control of the clutch volume indexes and it ran smoothly. Chrysler kept this top secret to avoid a recall.

The trans was so bad one very cold day our dealership sent a rental truck to Chicago and brought back 27 new ones. The fluid coolers got so cold they wouldn't flow and the trans melted down. Chrysler came out with a thermal bypass valve to fix that issue.

Nissan pulled a lot of super secret stuff to make their crap actually work right.

So, My 0651 isn't happy after the emissions TSB. Is it the sensors? I doubt that but they are reporting signals outside the scope of realm, so the ECU flags them and the dealer just keeps replacing them. So why the issue? It seems so obvious to me, the air/fuel ratio is unacceptable to the new ECU parameters. I believe widening those sensor parameters would keep the Mil off, while allowing the new A/F ratios from the TSB reprogramming to scrub the NOX acceptably.
Of course, running the emissions system outside of printed specs is emissions tampering. But that's debatable, if the emissions are within the spec isn't all good? So a traveling, secret agent tech may have a PCM flash to fix this issue, not in print anywhere and NOT shared with dealer techs.
If I could get my hands on a star diagnostic data link, I'd look into widening the parameters myself. Just look at how easy it is to tune VW's with Ross-Tech software.

 

Yippee! Picked up my 2014 E250 from Ft. Pierce Mercedes this morning. A brand spanking new Cat And both NOX sensors. Got to love their determination.
When the warranty runs out, good bye emissions system. Let it Flo.

 

CEL back on yesterday. P20EE stored. Dealer took car in yesterday and after 2 hours they told me they need to do more diagnostic. They put me in a loaner.