[Moosy]

Hi everyone,

Fresh BMW owner and more of a lurker in the forums here, trying to learn as much as possible from already posted threads through the years.

2/3 months ago picked up my first BMW, 2012 E91 318i automatic, has N43 4pot (yes, I know you are reading this with "oh brother.." expression on your face).

165xxxkm on the clock, chain done at 126xxx and genuinely looks well taken care off from inside and out, coming with a bulky maintenance record booklet and a lot of receipts.
Bought it with a pre-alerted thermostat issue, changed the water pump/thermostat (OEM), oil with filters and really enjoying driving it even though 4 pot is already feeling like constant "I want more buddy".

Anyways, couple weeks back my NOX sensor went fully dead I believe (codes 2AF4, 2AF2 and 2AF6 coming back few minutes after clearing them), and I can already see the increase in fuel consumption, went from around 8L/100km to almost 10L/100km.
That being said, already looking into repair, but still debating between OEM sensor or NOXem emulator.
No CEL light appeared at the time.

Yesterday I had to take a 35-40min drive, went on as usual, but almost at the end of my trip (as I went off the highway) CEL light appeared, no message on iDrive.
Stopped, scanned for codes, the usual 3 for NOX appeared, alongside a new 2AA5 code (DME: Exhaust camshaft, position monitoring).
While was checking for codes, I could feel the car shaking quite a bit on idle, but mostly in P/N positions, couldn't really feel it while standing still in D. No RPM jumps, constantly at around 650.
After clearing all 4 codes, CEL disappeared, shaking was still bit noticeable but almost gone.
Today basically same thing, 30min drive, CEL appears, same 4 codes. Cleared and went on the rest of the drive without issue.

What would be the first things to look at here? No oil or coolant loss/leaks, values stay as it should. Solenoid or maybe a sensor? Read somewhere that 2AA5 normally doesn't come up by itself and is more of a "DME is reading something wrong" code - highlighting other problem?
Willing to learn as much DIY with these cars and would really appreciate if someone could guide me where to start, or/and highlight the most common points of failure.

Thank you all in advance.

[Moosy]

quick update, 2AA5 code is completely gone and doesn't come back. 2AF4, 2AF2 and 2AF6 always do though.
is it true that faulty nox can cause rough idle but no other noticeable symptoms? was also reading that sometimes changing nox sensor won't fix rough idle if cat converter sulfur level is high?
what would be the first checks for me to do so to decide if i go for OEM sensor or Noxem?

[Bony6777]

Hi mate. When you have error codes it's great and potentially codes can direct you towards issues your car have, but you need to remember that codes you have might be only a way car telling that something is not right. NoX sensor is very last on the line of emission control. Before NoX that is 2 labda sensors, temperature sensor, injectors, PCV valve, MAP and MAF sensors. Your needs to read real time data to have better understanding on why engine running rough. Have you checked real time values from all those sensors, have you checked smoothness values for your injectors? All this needs to be checked.
Also if you or previous owners was using car only for small journeys your NoX will be full of sulfur and to clean it up you need to take a car for good drive on the motorway and to drive for about 40 minutes at minimum speed of 110km/h. There is lots of videos on YouTube where people showing which values need to be checked via diagnostic tool to see if this driving burning out sulphur build up.
I have myself 318i 2011 with 95k miles on the clock. NoX still original. Had issues with NoX. Tried first to burn sulfur build up, values gone down but idle still was rough. Sorted out issues with NOx by replacing injectors and MAP sensor. Injectors was leaking and MAP was giving false readings, in result fuel/air mixture was wrong.