experimental MAF reset switch: which circuit to interrupt? more complications

[X5chemist]

Are P0171 and P0175 the only codes now? If so, I don't think the MAF is causing them. The second bank is getting too much fuel. The extra fuel is causing rich fuel trims. Have you OHM the injectors? "This code will set when the ECM can not compensate for the amount of air or fuel required to return the air fuel ratio back to the set parameters." It's not happy with something on bank 2. Cylinders 4,5, and 6.

[workingonit]

No, I'm not getting codes anymore (but I would have, if I had kept using the Siemens-VDO MAF that went wonky during the test run back on Sept.7,2024).

Also, no bank2 is lean like bank1. It was always P0171 & P0174 (not P0175) that I had been getting. Never a rich code.

[X5chemist]

Oh, so the X5 is code free? I'll send you the OEM MAF today. Please let us know how it works after all emission tests are passed.

[workingonit]

Originally Posted by X5chemist

Oh, so the X5 is code free? I'll send you the OEM MAF today. Please let us know how it works after all emission tests are passed.

I passed emissions testing back in October, after resetting the fuel trims to zero, by unplugging the MAF, and quickly running a drive cycle on the way to the inspection station (all monitors, except EVAP, reset within 10 miles).

The cheap $20? MAF I'm using never lets the fuel trims get into the range where a SES /MIL light is set, but i wasn't taking any chances. Since i installed the $20? MAF, I've been resetting fuel trims this way periodically, and thus avoiding any limp-home situation. That's also why I started this thread, because I wanted a way to either reset the fuel trims or tune the MAF's signal to the DME from inside the truck, in order to workaround having to unplug the MAF itself (hard to do, when in traffic, or in the rain).

I'll inform you of the results after testing with your OEM MAF, in this thread. Got my fingers crossed!

[workingonit]

from 2/1/25

Originally Posted by X5chemist

...I'll send you the OEM MAF today. Please let us know how it works....

and

Originally Posted by workingonit

...I'll inform you of the results after testing with your OEM MAF, in this thread. Got my fingers crossed!

update from 3/15/25

Originally Posted by workingonit

...I haven't been driving much at all, during the last six months (except for a couple of trips to the ranch, at 80+ miles each, and a few short trips to the store, inspection station, and the tax office (voting and car registration renewals), due to:
1) my wife loves driving her Lexus more than riding in my X5 (seats are too hard!),
2) I was really sick from Xmas until just recently, and would sometimes get into coughing fits, so I thought it wise to not drive at those times, and
3) I tore the Piriformis muscle in my hip, on Dec.23, and because it affected my walking, it was followed by peroneal tendonitis in my leg (both on my right side), so it is uncomfortable (to say the least) to sit and drive.

update from 3/22/25

Originally Posted by workingonit

...About the OEM MAF: I have only made one very short drive in the X since you sent me that MAF (thanks again!). I've been pretty sick since mid-December, and also had a lot of pain with my right leg (popped the piriformis muscle in my hip, also in mid-December, and that caused a resultant strain in the peroneal tendons) so I have trouble sitting straight up in the seat to drive.

My illness has now passed, and I'm getting used to the pain in my hip & lower leg (can walk without a cane, again), so I can drive again.

During the short trip earlier, the fuel trims seemed to be slightly better than previously seen, but I haven't driven enough miles for the trims to equalize, yet.

I plan to drive the X next week, and see what the MAF does on a longer test drive circuit (including a highway component), that I follow when getting stubborn emissions monitors to set.

Ok, I finally drove the X5 again today, only the second (very short) drive since I received the OEM MAF in February. Total miles under 25. My bad hip & leg problems have made me a passenger, until today, when I HAD TO go get some gas for the mowers (old Dixon zero turn, Husqvarna push, Cub Cadet push string trimmer) while the wife was out and about doing wife crap. Need to cut the wilderness out front (lotsa grass and a drainage gulley with a full jungle in it).

The hip and leg problems will not keep my wife from insisting I cut the gulley, while she gets to operate the zero turn riding mower, so I will probably remain in pain for the foreseeable future; but as far as driving/testing the OEM MAF goes, I'll just have to see how it goes, too.

I don't see any long distance driving oppportunities in store, so if I'm to give the OEM MAF a fair test, I'll just have to do a long test drive, for test's sake, only. But, the two short trips so far have shown the LTFT's between 3.12 and 7.2, with STFT's doing a balancing act. Nothing has radically changed from past results.

G/S is still nominal, and O2 readings show a lazy reaction to throttle inputs, as usual. I even tried a full throttle acceleration from 10 mph (first ever in the X5, for me, aware that my transmission is quite elderly), and only then did I see larger Short Term numbers, and faster O2 reactions. Not sureif that's good or bad.

Hopefully, I'll get on the mend this summer, and finally find what's been ailing my X5, as well. Stay tuned.

[X5chemist]

The ECM will need miles to relearn. Keep driving it. 01 vs 06 MAF may or may not have different ECM fuel maps. Hopefully the engine light will stay off.

[workingonit]

X5chemist- Latest report on the Siemens MAF you sent:

I put in a 101 more miles yesterday, about 60% highway at speeds averaging 75 mph, and 40% at speeds averaging 45 mph. The O2 sensors were acting normally, as was the MAF reading in grams per second, and the LTFT's settled in at 5.47 to 7.03 for both banks on the first half of the trip (on the way down to the ranch, driving conservatively), but became elevated to 8.12 during high-speed and rapid speed changes during the first half of the return trip home (see this https://xoutpost.com/1245027-post1116.html for further info).

The LTFT's started falling back to 7.12-7.57, IIRC, during the relaxed driving, on the last quarter of the trip.

I'm assuming that the DME is trying to learn from the MAF sensor, and though it came from an '06 to an '01, it has the same PN, and listed as the same for both years as OEM; despite very few miles (comparative) on it vs. the cheap MAF's I have, the Siemens isn't reading as high numbers on LTFT's, nor of course the ridiculously high readings that my former Siemens MAF did (now dissected for science).

More testing/driving to come.

[X5chemist]

Nice run. What were the short term fuel readings? Are idle short term fuel trims near 0?

[workingonit]

Originally Posted by X5chemist

Nice run. What were the short term fuel readings? Are idle short term fuel trims near 0?

The STFT's were ranging from -10 to +8, depending on speed, grade, load, while the LTFT's at idle were hovering near zero (+/- 3). Better than before.

I'm still planning to replace all vacuum lines (though no leaks have ever been detected), and perhaps even install another fuel filter/regulator (though the PO said he installed a new Bosch regulator just prior to trading the X to me).

I think maybe the fuel system isn't supplying enough fuel at times, with constant positive LTFT's. I checked the fuel pressure at the Schrader valve, and it read about 50 psi, but that was a few years ago.

I'm needing to check the injectors, and one of my Android apps (Bimmer-Tool paid version) shows injector balance, so if one or more "Bremi" injectors is lagging, it should show that. Do the Foxwell NT500 series scan tools (mine is a NT510 Elite) have any tests or bi-directional control of the injectors?; if they do, I must've not found it on mine.

[X5chemist]

-10 + 8 = -2 Close enough to zero when summed together. +/-3 = 0 Not bad for an old M54. Run a strong fuel injector cleaner through it. One thing M54s like is long drives and high RPMs. Put ya foot in it!