P0171 and P087 Codes for N55

[resistro]

2011 535i has low power, long start, and stalls at a stop sometimes. Does NOT feel like it's miss-firing and no misfire codes.


CEL on w/ P0171 and P0087, low fuel rail pressure and lean bank. There is so much out there on the HPFP and the LPFP having issues that it has my head spinning. Not to mention the fuel pressure sensors have issues too. Trying to determine a plan of action to diagnose the correct problem without replacing all three parts?


I am getting DMTL short to positive codes also, but I think it's unrelated to my fuel pressure issue.

[MarcoZandrini]

The P0171 code means bank 1 (cylinders 1-3) have a vacuum leak or leaks. The best way to find all of the vacuum leaks is to professionally smoke test the intake manifold. Start there.

[White94RX]

Low fuel pressure will also cause a lean code. And since you have a fuel pressure fault code, I'd think that that would be the reason for the lean code. Lack of fuel pressure. I'd probably be replacing the HPFP.

The DMTL code is unrelated, but it is required for emissions, so I'd be replacing the DMTL pump as well.