My Diesel Exhaust Fluid experience - 8/2011 X5 xDrive35d

[josiahg52]

Originally Posted by fullmetaljacket

Sorry, Did not want to start a new thread on DEF. Just got warning messages level 2 (200 miles to go) with no level 1 (999 miles to go). Plus the warning message...

"Incorrect diesel exhaust fluid added. Please note the remaining driving range! if driving range reaches 0 miles/ kilometers, engne start will not be possible. Have the system checked by the nearest BMW center".

My initial guess was a low DEF level so I did a a DEF refill/top up. Both active and passive tanks drank around 17 liters (One 10 liter jug and 70% of another 10 liter jug of BMW AdBlue DEF).

The warning messages did not disappear! :-( So I did 2 scans: Foxwell NT510 and Carly. I was able to get identical error messages which could not be erased/ cleared...

0041F9
DeNOx system, plausibility

00474C
DeNOx system, warning and Abschaltszenario

004748
DeNOx system, warning and Abschaltszenario

I did a quick research on this issue from various forums and found out that this might be a NOX sensor related issue and not a DEF level issue since the sensor inside the DEF tanks only measures DEF level and they do not determine whether the DEF is good or bad quality. I'm going to the a BMW certified shop this weekend to have this checked since I only have 188 Kilometers left. I'm just soliciting thoughts, information or comments you might have regarding my theory before I go to the shop.

You are correct that the system can't sense incorrect fluid. It's can monitor NOx emissions and if they remain high after several hundred kilometers even with normally adequate DEF injection rates, the error message and/or DTC is issued. Checking the NOx sensors is a good start. "NOx System Inefficiency" DTC is 004D16, FYI.

[fullmetaljacket]

Originally Posted by josiahg52

You are correct that the system can't sense incorrect fluid. It's can monitor NOx emissions and if they remain high after several hundred kilometers even with normally adequate DEF injection rates, the error message and/or DTC is issued. Checking the NOx sensors is a good start. "NOx System Inefficiency" DTC is 004D16, FYI.

Thanks for the insights Josh! Now I did some more scanning using Foxwell NT510 to dig into the NOx sensor condition and found out the following:

1. NOX Concentration I (determination> 10 minutes driving!) 60.97 ppm

2. NOX Concentration II ( determination> 10 minutes driving!) -0.02 ppm

3. Status Signal NOX sensor I: Released NOX concentration can be read out

4. Status Signal NOX sensor II: 0

Does this actually mean that NOX sensor II is the culprit? Which one is sensor 2 and how do I locate this? Planning on doing more research on replacing the NOX sensor and hopeully I can DIY it...? Exciting!