[AgeUncaged]

Hi All,

First time poster here. I just wanted to share my experiences with my alphabet soup of carbon build up related trouble codes, mainly:

P2201 "NOx Sensor Circuit Range / Performance Bank 1"
P20EE "SCR NOx Catalyst Efficiency Below Threshold Bank 1".

In addition I am dealing with fuel injector offset codes (on all but one cylinder). I'm currently at 97k miles, and I've had a walnut blasting done once already at 54k. Hopefully this will give others an idea of the proper course of action to take when dealing with similar situations.

I decided I was finally going to start addressing these issues, so I take my car into the dealership in the morning. I tell them I'm aware of the NOx trouble codes on my car, and that I would like to see if they could replace the NOx sensors under the extended emission warranty (10 year / 120k miles). At the end of the day, the SA calls me. Bad news. They cannot honor the warranty to replace the NOx sensors because of the said fuel injector codes. Their advice is to clear all other codes until only the NOx sensor related codes remain. Only then will they replace the sensors. They waived the diagnostic fee (thanks!) and send me on my way (good luck!).

My take-away here is that this is obviously a complicated web of inter-related problems. I tried to pick the lowest hanging fruit, but I guess it doesn't work like that.

My next step is that I will start with a carbon cleaning and see that clears any of the injector codes. If that doesn't work, then I will have to throw fuel injectors at the problem. Hopefully it doesn't come to that.

[Pierre Louis]

As I recall, updating the DDE firmware may clear injector codes. I had a 2011 335d and for what its worth, there were several updates to the DDE for this model and several people had their injectors replaced only to find it wasn't necessary, but the DDE update fixed it.