Troutabout

Just bought a used MB. I am getting a permanent code P203D that says "Reductant Level Sensor Circuit High".

Does anyone know what I need to do to fix the problem causing the code?

Plutoe

I know of no correct cross sheet for the OBD vs factory fault codes for the Bluetec,however if you define the word reductance and it's relationship to your emissions process, I would say you have issues with your DPF filter system---to confirm you need someone who can scan the car with factory or equal diagnostic software to correctly determine the fault.

However wait, you are going to get spammed with all sorts of HS---be watchful,especially of you know who---ole PJ and his ford truck emissions stories!

kajtek1

Instead listening to clowns on this forum you can go to forum where those clowns are baned.
http://www.benzworld.org/forums/w203...ise-p203d.html shows the same code with different explanation.
With new technology sometimes you might be the first to break the ice and dealer might be the only solution.
Don't you have warranty on the car?

visual_image

Troutabout,
Had same code from my 2012 E350 Bluetec 6 months after buying it CPO. It was still under warranty and it took the dealer 3 tries to fix it. Basically it is your NOx sensor that is giving you that code. Unfortunately, there are two of them. Dealer guessed wrong the first time, went to left field with the second time, but got it right by replace the other NOx sensor the third time. Problem been gone for 1 1/2 years now. A technician from a different dealership told me that it was common with the bluetec, that he had to do that a lot. He said the new sensors are better and they need to update the software for it.
So I agree with kajtek1 about taking it to the dealer, especially if it is still under warranty.