F15 X5 35d P0172 running rich, P2002 DPF plugged

[419nickd]

Hello, I recently bought a used 2015 X5 35d with about 130k miles. Note that this should be essentially the same as a 30d in Europe. I've tried to research the codes, and I've done some diagnostics in ISTA+. Nothing has shown up faulty. The only fault is that the MAF reads close to the upper limit threshold, but it still passes.

Soon after I bought it, the CEL turned on. A quick scan showed P0172 (too low oxygen in exhaust?), and P2002 (Diesel Particulate Filter Efficiency Below Threshold). I also coincidentally did an oil analysis right before these errors popped up, and it showed a small but measurable fuel dilution problem.

I think I approximately get the economy that it should (29-30 mpg, or 7.8-8.1 l/100km) for mixed highway and urban driving. It also has approximately the power that it should.

My theory is that it has an injector that's leaking and spraying or dripping fuel continuously. Depending on the way it's leaking (drops vs. spray?), it could be sooting up the DPF, causing it to run richer than expected, and diluting the oil. Engine smoothness test in ISTA showed the injectors were all surprisingly good.

It runs quietly and smoothly. I would expect it to run roughly if it was very bad with a bad injector.

This is on top of the SCR system passive tank not working as it should, but I'm ignoring it for now because the active tank is fine and just needs refilled more often.

I had an e39 530d wagon for 12 years with 280k miles. That engine was bulletproof, but if it had any problems, I knew exactly what to do with it because it had half the sensors and was largely mechanical in comparison. I'm very disappointed with this N57 and I have no idea where to even start with it.

I'm hoping someone will have an idea of what I should do to at least start with, and how bad it is for the engine in the meantime. I suspect it's not good long term, but short term it's not completely catastrophic?

[RED_Y_]

Since you use ISTA already you should have all troubleshooting suggestions in the APP. I think you are already out of your federal emissions warranty.

[Clifton]

Spit-balling ideas - with a P2002 (Diesel Particulate Filter Efficiency Below Threshold), is it possible that your DPF is simply clogged due to age or excessive city driving? The clog is in turn causing issues further up stream? A bit like the old banana in the tailpipe gag?

[419nickd]

I actually tried ISTA diagnostics. The DPF test showed the differential pressure to be significantly less than the threshold (roughly half), despite not having run a regeneration cycle in ~660 miles (I guess it was due for a regeneration cycle soon). I tested the O2 sensors and they gave "plausible" values based on the test cycle they prescribed in the software. I also thought that maybe if the EGR valve was stuck open, it would cause some of the errors. That also tested great, and since it logs position with respect to the requested signal, it should be able to self diagnose ok.

So I'm really puzzled as to why these errors are occurring. I'm wondering if there is a faulty sensor that only gives bad data some of the time, despite the various systems in the car operating correctly.

[419nickd]

And I appreciate your replies so quickly and I apologize for not replying sooner!

I expected to get notifications on replies, and that was not the case. I imagine there is a checkbox somewhere that I did not check...

[Browne2192]

Any fix for the DPF efficiency low code? I’m receiving this too with no indication of blockage and no decrease in MPG. Just annoying check engine light. Thanks.