X5D error codes 4D16 and 46A4

[Jeffkukuruda]

So my CPO warrantee just expired and at 100,400 miles I got these two codes, 4d16 and 46a4, and a CEL. I reset them and the codes stayed away for about a week. All the reading I have done points to either a dirty metering valve or a faulty aft NOx sensor which appears to be a $601.00 part and gamble at this point. Has anyone had this specific set of codes with a suggested way ahead?

Thank you in advance.

-Jeff

[ZetaTre]

With the premise that I have no direct experience with either of these two codes, one thing I noticed in my 35d at one point is that the NOx module is right below the drain for the AC condenser.

In addition to that it is also in contact with an insulating mat placed on the transmission cover. Said mat get soaked up with the condensation dripping (what is circled in red is the A/C drain).



When I inspected my module was showing some superficial corrosion which I went ahead and cleaned off.

Like you mention in your post, it wouldn't be the first time someone has a NOx code where the culprit is actually the NOx module, not the sensor itself.

My theory (just a theory, nothing more), is that condensation eventually makes it into the module and fries it (I also went as far as saying that the failure in the driveshaft is the result of the same combined likely with low quality bearings on the u-joints...). There was also some superficial corrosion on the transmission cross member.

In any case, I rerouted the A/C drain, removed the mat and drilled holes in the plastic cover so condensation doesn't puddle.



This may not be much help and may actually be totally irrelevant, but if in your quest you end up finding the culprit in the NOx module, I'd love to hear that and would love to see the condition of the module itself.

I wish I could help more...

[Jeffkukuruda]

Thank you very much for the insight! I'll be inspecting on a lift soon and will keep you informed.

[blue dragon]

The metering valve is also inexpensive. I've had to change mine already, so I'd try changing that before changing the nox sensor. Search for Rheingold on torrents, and run the diagnostic test plans

[ZetaTre]

Originally Posted by blue dragon

The metering valve is also inexpensive. I've had to change mine already, so I'd try changing that before changing the nox sensor. Search for Rheingold on torrents, and run the diagnostic test plans

Good point about the metering valve!!!

Blue Dragon and ninja zx11 did a great job documenting it and how to test the metering valve. You can read about it here: Reducing agent metering valve actuation fault. - Bimmerfest - BMW Forums

Note that the code for them was different, but I would still test it to see how the resistance of your compares to that of a new one.

[Jeffkukuruda]

Great info guys. I'll be trying that first as soon as the WX breaks this week.

[seattle]

Thought I would resurrect this thread rather than open new one.

2011 35d, 108K miles.

So, this code is lately persisting:

0046A4 DDE: NoX sensor after DeNox Catalyst, plausibility NoX

I have searched potential answers on forums, with potential causes being:
-Bad urea active tank
-Clogged SCR metering valve
-Bad cat
-Bad or fouled NoX sensor

Being fully aware that there is a warranty extension on Active Tank and Metering Valve, I need to make sure those are the culprit before heading out to dealer for claim (and risking wasted diagnostics fee).

So, pulled this fault code documentation in Rheingold:

Fault Description
Monitoring the NOx signal offset value (nitrogen oxide sensor downstream of SCR catalytic converter). The fault is detected if the average offset value exceeds a limit value.

Limit value: between 30 ppm and 60 ppm (version-dependent).

This is pure legalese!

Can one of the veterans help me decipher this text (calling you ard, Doug H., ZetaTre)?

This snippet:

NOx signal offset value (nitrogen oxide sensor downstream of SCR catalytic converter)

..is it safe to assume that "offset value = difference in reading between pre and post NoX sensor"?

Can it be said this way?:
"The fault is detected if the average detected NoX reduction (over certain period of time, on that below) between pre and post Cat sensor is less than 30-60 parts per million".

Continuing to read..

Condition for fault identification
Monitoring takes place continuously when the following preconditions are met:

- The difference between the maximum and minimum offset value must be less than the limit value during this minimum duration.

Limit value: between 4 ppm and 7 ppm (version-dependent).

...
[talks about engine rpm and other preconditions
...

I think it can be said like this in plain English:

"Non-stop monitoring will start as soon as largest and smallest difference between pre and post NOx sensors is less than about 7 parts per million.
In other words, system will start continuous watching as soon as it detects no improvement in NoX. "

The rest of documentation, more-less understandable.

Condition for fault memory entry
The fault is entered if it has been detected more than the following number of times (fault debouncing counter): 1

Action in service
Check the NOx sensor downstream of SCR catalytic converter with an SCR catalytic converter system check.

1. Check line and plug connections
2. If wires and plug connections are OK:
Replace nitrogen oxide sensor after SCR catalytic converter.

Next, hooked up laptop and went for a drive to :
1. Confirm post-cat sensors working
2. Gather live NOx sensor data under various driving conditions

Observations:
40 mph on cruise control, 1,500 rpm, UPHILL
pre-cat: ~600 ppm
post-cat: ~200 ppm

40 mph on cruise control, 1,500 rpm, LEVEL
pre-cat: ~110 ppm
post-cat: ~50 ppm

0 mph, 800 rpm, IDLING
pre-cat: ~130 ppm
post-cat: ~12 ppm

If it means what I think it means, I may have hit this "Limit value: between 30 ppm and 60 ppm" on this test drive:

40 mph on cruise control, 1,500 rpm, LEVEL
pre-cat: ~110 ppm
post-cat: ~50 ppm

If that's true, I need to get to the culprit of worse-than-expected NoX readings after SCR.
They could be:
-DEF injection issues
-Bad Catalyst
-Bad NoX sensor. Which one?
For example, pre-SRC sensor could be fouled by soot, giving lower initial readings and thus misleading post-SRC sensor...

It doesn't help that there's no information available for NoX reduction baseline in well-working SCR system in 35d.

Any info is appreciated.

[ingenieur]

Since you have Rheingold - perform the SCR system function test just as the dealer would/
1. Test of the metering valve
2. Function test of the SCR system - takes approx. 45 minutes

Most likely an aging NOx sensor - if so replace both.