13' 35d DeNOx low efficiency
 

My 13' 35d has been throwing the following codes, I've cleared them and they continue to return after 100 or so miles.

DeNOx system efficiency efficiency at low - 004D18
DeNOx system efficiency: efficiency is too low in the range 1 - 0042FC

Does anyone have suggestions on where to start? I'm new to diesels and DEF.

The NOx catalyzer is in the mid pipe. There is a sensor before and after. I would suspect an issue with the post-catalyst sensor before I suspected an issue with the catalyzer itself. Assuming there are no codes for the urea injection.

No codes for urea, anyway to confirm the sensor is bad? I recently had a NOx sensor replaced under a recall, I'll have to find my paperwork to see which one it was.

INPA or another diagnostic tool with live data should be able to sample the sensors so you can see if it's just flatlined or gone out of range.

Continuing where we left off, I went to the dealer and they flushed and refilled the DEF & confirmed spray pattern was good. Today were getting an incorrect DEF fluid, 200 miles until no start. This is the first time I have gotten this error and it seems to be a result of the flush\refill, do I dare go back to the dealer? Anything I can do to confirm besides checking that they filled the fluid?

That error could easily be caused by the same sensors. I would insist that they replace the pre and post cat sensors if you have a warranty.

I'll have to confirm the warranty status tonight.

Check out post #7 here:

Incorrect Exhaut Fluid Message! - Bimmerfest - BMW Forums

Possibly is the catalyst. I guess they have been known to go bad. But I believe the sensors are much cheaper.

That would be a heart breaker, any chance the SCR cat is covered under warranty?

There ought to be a little pamphlet in your glove box called "the warranty"...perhaps give it a read?

Or go to BMWUSA and find it

There is an extended warranty and/or recall campaign. But I'm not up on the details.

Below are the codes I pulled with Carly.

DeNOx system efficiency efficiency at low
Code: 004D18

DeNOx system efficiency: efficiency is too low in the range 1
Code: 0042FC

sorry, unknown fault
Code: 0041F9

DFC
Code: 00474C

DFC
Code: 004748

Not in warranty, BMW is recommending NOX sensors. I did get Rheingold working last night and was able to read vehicle information. It sees the codes, I'm just not familiar with it enough on how to use this as a diagnostic tool. It seems the upstream NOX sensor is most likely the culprit based on others experiences, anyway I can confirm this via Rheingold before I drop 500-600 on the sensor?

The DEF tanks are under an extended 10yr/120k warranty and if you are under 70k I believe the emission systems are covered under federal emission standards. If you are eligible I'd look into it before pulling out the wallet.

I just had to have mine replaced. My rear nox sensor was bad, then the scr had to be replaced. Next time I'm removing it.

Very similar codes btw.

I'm at 75k, I think some states mandate 8y/80k but I don't believe Wisconsin is one of them.

Why not read your warranty??????????????????

Federal coverage on the CAT is 8/80k

I understand the cat would be covered, but it seems the dealer thinks the NOX sensors should be replaced next. I'm just trying to confirm this is a valid next step, and diag myself.

Sent from my Nexus 5X using Tapatalk

I have heard that there is a good chance its not the sensors even when it says it is.

local guy wanted to buy my nox sensors but when he swapped the sensors with someone else with an x5 it still gave the code. can't remember what his codes where but it pointed to the nox sensors.

its confusing because the cat apparently has its own code that should go off but apparently it did not.

there could also be corrosion on the harness going to the nox, or not sure if this is possible but some said a bad battery could cause it.

so who really knows!

Replaced front nox sensor, still have the issue. Will be replacing rear sensor next.

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Did you or the dealer run the diagnostics for the SCR system?

Adblue quality test with a refractomer - must be 31.8 => 33.3 %

Check the metering valve for crystallized Adblue

Make sure the dosed quantity is right - perform the 50 minutes ISTA function test to check the NOx sensors and SCR catalyst efficiency?

madbim,
Did you ever sort the cause of this code?? Seems I am going down the same path with my 2013 X5

replaced both Nox sensors, reset Adblue level went for drive on interstate.

Thanks
will try that

BMW just recently extended the warranty on NOX sensors you should check to see if your covered.

Put your last 7 of your vin in here:
http://www.bmw-rp.com

Let us know if you have it, for my 2011 x5 35d it doesn't show nox?

I'll have some used NOx sensors available soon. I'm right in the middle of my delete.