McGG

Due to some managing of a 3rd party extended warranty and a disagreement with the dealer over the price of parts, I found myself at a reputable independent dealer in town.

The CEL code is for a new NOX sensor, and the indy says he can't do the work because to re-code the car, he needs to have a "live data connection" to the MB head office, and only the dealers have that.

I'm assuming he was referring to the most recent version of Star Diagnostic.

Am I getting fed a line?

Is there work that can ONLY be done at the dealership?

joshd2012

That seems a little suspicious. Have you tried calling another mechanic? Or one that specializes in German vehicles?

alx

easy with that one.

what are the codes?

generally when the nox sensor misbehaves there is an underlying reason which if not found will continue to throw nox- related codes and/ or appear as the sensor is bad.

there are many coding procedures which require "authentication"/ validation from the star/ das mothership and thus pirated versions of star/ das cannot do.

McGG

Yes, after more research it seems that I think he was referring to SCN coding.

I'm sure what the actual codes are, to be honest.

What are some of those issues?

alx

"nox out of bounds" codes are usually related to carbon build up and other similar engine asthma-related conditions

the freeze data will show why the codes were thrown and if nox is bad or just reading out of bounds

McGG

carbon buildup?

that doesn't sound good. Maybe I should get my warranty claims department to start warming up their keyboards?

drgeeforce

P204F or P2201 sounds about right. If there is ANY factory warranty issue, MBUSA has to be contacted. But what is confusing is the "Third party"? If the third party is paying for warranty claims, your indie only has to get authorization from them. The codes are entered into Star to maintain factory warranty, because most emission controls are covered by MBUSA 2-years or 24,000 miles, whichever comes first. In addition, specific emission-related components like the Nox sensor are covered for 7y/70K, and the SCR is covered by 8y/80K.
I agree it may be carbon build up due to slow acceleration and excessive city driving, remedied by mashing the pedal at the freeway on-ramp occasionally and long distance trips.

http://www.mbusa.com/vcm/MB/DigitalA...on_booklet.pdf

alx

unless more data is available those are (well-founded) speculations...

we really need more data before pointing you in any particular direction.

McGG

I didn't actually get the codes...i guess I should have.

McGG

Here is what it says on the dealerships report:

"81239 CEL is on. Check Codes- 134V00 Lower limit of upstream Nox sensor reached, along with 3 other upstream Nox sensors are stores in the CDI control unit. Fault Trace codes. Internal electrical fault is present in the upstream NOx sensor. May possibly be other issues but need to start with upstream Nox sensor replacement. "

Maybe I can the dealership to give me the exact codes that they are referencing.

alx

I would reset engine adaptations, erase codes, and do some aggressive driving. If code reappears then replace said nox sensor and take it from there.

McGG

So the other codes might actually be GOOD news? Thanks so much.

Engine adaptations? Do you mean mods?

And can I erase codes without a C3/C4?

BTW: your help is greatly appreciated....I've used a number of your posts as reference since I got this vehicle.

alx

Thanks. I wish we had more folks willing to help a bit. I know there are some very knowledgable people here that for one reason or another prefer to not help even with simple advice that in no way affects their bottom line.

Yes, codes and engine adaptions can be reset with c3/c4. It is in the engine management module.

The codes for broken sensor is usually "signal implausible" error confirmed by looking at the freeze data. Not seeing that message in your post. So, you still might have a dead sensor, but i would try some simple steps before starting to replace parts.

McGG

I'm going to order up a c4 then....thx

drgeeforce

Biodiesel also causes Nox upstream values to be higher.
A faulty EGR can cause Nox to rise.
A loose timing chain can cause MAP to add more fuel increasing CO making the gas analyzer to read more Nox.
Conversely, if the timing is too advanced, preignition will make Nox.
Exhaust valves if scored with carbon will release more Nox.
The Star C3/4 costs $300+.
A $50 OBD will give you better info for the money

McGG

Ok, here are the codes from my brand new C3 from Shardul:

134C00 - The lower limit value of component NOx sensor upstream of SCR catalytic converter was dropped below/not reached.

135400 Short circuit in component NOx sensor upstream of SCR catalytic converter

149C00 Component NOxsensor upstream of SCR catalytic converter is not operational

153600 Component NOx sensor upstream of SCR catalytic converter has internal fault.


Sounds to me that it's more than just a carbon thing?

drgeeforce

from Captain Obvious:
Sounds like to me your "NOx sensor upstream of the SCR catalytic converter" is out.

McGG

Sounds like you sometimes can get false positives on these things.

drgeeforce

What year is your vehicle? NOx sensor is emissions related, it is probably still under warranty. In CA we get 7y/70K. http://www.mbusa.com/vcm/MB/DigitalA...on_booklet.pdf
see page 43.

If Dealer says no go, I'd try what alx recommended, reset, drive it hard for a week see if it resolves the DTC.
If you're a DIYer I sometimes use getmercedesparts.com. If you're feeling frugal, try aliexpress.com/store/group/NOX-SENSOR/

McGG

I exported the car to Canada, so I'm not sure if the emissions warranty would still be in place or not.

Would driving it with a broken N0x sensor (assuming the worst), hurt the vehicle?

Mine is a 2012.

drgeeforce

If you only moved, the car is still under emissions warranty. Check with MBCanada.

Clean-Diesel has three parts, the particulate filter, the oxidizer, followed by the reducer.

Driving with a faulty NOx sensor could damage the Selective Catalytic Reduction (SCR) causing you to lose the clean-diesel aspect of TDI.
1. if the sensor misreads the upstream nitrogen oxides as high, this forces more urea (DEF) to be used in the SCR, any excess will corrode the catalyst.
2. if the sensor reads the stream as low, then it uses less DEF, releasing more smog into the atmosphere. It also overloads the catalyst with substrate and the feedback loop to the oxidizer will cause it to overheat or melt.

alx

you need to reset the codes clean and log some data when they get triggered. this will show you if the sensor is bad (ie you get short/ infinity on the sensor) or you have another problem and thus the nox values provided by the sensor are out of range (but "move" in time correctly).

mike278

If the code was only for a sensor range issue, then I would suggest soaking the adblue injector overnight in distilled water. Those things get crystallization in them from the urea in the adblue. Since it is showing an internal fault, then it probably does need the NOx sensor. I'm pretty sure you don't have to go live with MB to code anything. If you do, you can get a one day use for StarTekinfo that will let you code and program with the SDS/DAS.