[tsykal78]

I had similar experience with the "incorrect fluid" message in my 2014 X5. Maybe someone will find my story useful in their troubleshooting experience.

All 4 codes as mentioned in the original post above were registered with 200 mile no-start countdown. The error message did not make sense at the time since AdDlue was refilled ~4 months prior to that, how could it become incorrect? But I was a lucky, because the error message disappeared in about ~120 miles of continuous drive (on the same trip).
My initial thought was maybe because my AdBlue was not fresh, and because of the higher summer temperatures it somehow deteriorated. So, when I got back home, I just added 2.5 gal of fresh fluid into passive tank and called it fixed.

In about 2 months (~5k miles) the same issue re-appeared again.

The first thing I did this time was tested the Adblue using refractometer: syphoned few drops from the active tank (using ~3 feet long, .25in dia tube). It was within the specs! I also took a sample of brand new fluid from BMW dealer - this one was actually 0.5% worse than the old one from my tank (yet both were within the spec).

Some forums suggested dirty NOX sensors. So, I removed them to soak in Lucas Injector Cleaner. Although the sensors did not look that dirty.

Also, removed the SCR metering unit, it had small amount of white deposits on the nozzle (i wish I took a picture of it), but it was not that bad either. I cleaned it with water and re-installed everything back.

Went for test drive about ~40 miles. The countdown still there, but now I got two more codes related to upstream NOX sensor: 2A7C00 and 26ED00. It could be that the cleaning mess-up the sensors, not sure...

Then I decided to get ISTA+. Took me few days to set it up and figure it out.
I was surprised to see that the first thing in this scenario the dealer mechanic is instructed to test the fluid using the same refractometer (not just blindly replace it and flush the system as mentioned by some) . So, this test is all about the correct ratio. Now, the deteriorated fluid theory in my case was less likely.

Using the ISTA+ software, I was able to test SCR metering unit, the spray looked good, and the amounts were within 24ml (+-20%).

ISTA+ also has a procedure to test the NOX sensors by idling the engine ~10min in higher RPM. Both NOX sensors registered values (~64ppm & ~57ppm). I still don’t know if these values are ok. I don’t know what “offset value” or “Limit value” is, which is supposed to be 4 and ~30ppm according to the ISTA instructions. But at least the sensors were not dead.

At the end I reset the adaptations and let the “vehicle to go to sleep” (still not sure what that means). Started the engine the same problem still there.
Then I went to erase all the error codes and reset the adaptations again. Turned off the ignition for few hours to let it “sleep”. Then started the engine, the check engine light was off, but the countdown was still on, and only 1 or 2 of the old codes were still present.

Then I remembered that BMW performed some recall work on my SCR a while ago, and they send me some follow-up letters. To my own embarrassment one of those letters stated that my NOX sensors had extended warranty to 8 years/120k miles.
So, now I decided it’s time to surrender to the local dealer. Who knows, maybe they will replace the sensors it would fix the problem. Plus, I had not too many miles left on the countdown for farther testing.

On my way to the dealer, I took highway route, at exactly 21st mile of continuous drive the countdown disappears!

So, now I am not sure what to do. Maybe the metering unit nozzle was the reason, and my first test drive did not do it because I did not have ISTA to reset adaptations. Or, maybe I should get the NOX sensors replaced while still on warranty, but how would I make the dealer do it?... to be continued.


3 months update:
When the countdown and check engine light cleared themselves after 21mile continuous driving there was still few codes left in the memory, one of them pointing to bad front NOX sensor (2C4E00, 29FB00, 29FC00, 280D00). Having the extending warranty proof in my hands I boldly took the car to the dealership, they ran their diagnostics and agreed to replace both NOX sensors. Although, it took them an extra day to reset adaptations and to ensure everything is set. Everything was covered by the warranty.
After ~3months/10k miles - no codes, no issues.