I am now having an issue with my 13 R56 N18 after a fuel filter change. I now have a P0171 code showing after replacing my fuel filter. Hooked up OBD2 and monitored all of my sensors applicable to this issue. At the time the issue started I had also replaced the PCV valve on the valve cover for piece of mind. A few days later the CEL came on ran diagnostics and got the P0171 System Too Lean Bank 1. So I removed the new PCV and installed the original cleared codes and didn't have anymore issues. Stopped to top off with fuel and the next day received the same code. ST Fuel Trim is around 0 at idle and LT Fuel Trim is at 28. When load is applied (2200 RPM) STFT & LTFT are within the specified limits of +/- 10%. Once back at idle trims return to previous values before load. Replaced complete fuel filter housing reset codes and still having the same issue. MAF sensor is showing 8-8.8 g/s, have done an air leak test and no leaks were detected. Will be cleaning the MAF tonight to see if the readings come back down to normal values. Also monitored the fuel rail pressure and at idle it is maintaining a 1100 psi as it should from the research I have conducted. And tips would be greatly appreciated.

 

Also had another question. Does anyone know what this sensor is for and why it isn't hooked up. Thanks