2011 X5 35D DPF issues

[Jrosh1223]

Hey everyone, had a question about some issues my daily (2011 X5 35D) is experiencing. Scanned for codes/faults using my Foxwell scanner, and the codes I picked up are:
P0471- exhaust pressure sensor ‘A’ Circuit range/performance.
P14A7- Diesel Particulate Filter System Flow Resistance Too High
P244B-Diesel Particulate filter differential pressure too high bank 1.
P0299- Turbocharger ‘A’ underboost condition
P244A-Diesel Particulate filter differential pressure too low bank 1.
Ended up clearing the codes present a while back and forcing a regen via my Foxwell scanner.

Had the DPF cleaned (Process was performed without removing the DPF). In addition to the cleaning, I replaced the exhaust pressure sensor and the pressure hose. Despite the aforementioned, I am still throwing codes (4CF3, 4D01, and 4D99) and have a CEL. Readings from the exhaust pressure sensor are indicating negative pressure, but the tech who performed the DPF cleaning also pressure tested the DPF, and ruled out the DPF being damaged. I’m also experiencing a strong smell (diesel) when the AC/heat is on. Any ideas?

[wcs531]

This thread on e90post suggests negative pressure could be as simple as the hoses for the differential pressure sensor:

https://www.e90post.com/forums/showthread.php?t=1041289

[Jrosh1223]

Thank you for the response. I’ve already attempted to replace the DPF pressure hose and exhaust pressure sensor, however, the aforementioned codes and CEL in conjunction with the negative pressure readings have persisted.

[wcs531]

Originally Posted by Jrosh1223

Thank you for the response. I’ve already attempted to replace the DPF pressure hose and exhaust pressure sensor, however, the aforementioned codes and CEL in conjunction with the negative pressure readings have persisted.

I guess I meant to say I would triple check those hoses on the differential pressure sensor. On the x5 there is also an additional EGR that comes off the DPF and goes to the big turbo - and now that I think about it I am not sure how this works at all. I would think it is only engaged when exhaust is routed to the small turbo? So if that is stuck open while the big turbo is being used then air may bypass the DPF? (Just thinking out loud).

I would think negative pressure would indicate more pressure after the DPF, so in my opinion either:

A) Loose/cracked pressure differential hose before the DPF
B) Lower EGR stuck open causing exhaust to bypass DPF, thus creating more pressure on the downstream side. (Does the exhaust smell happen at idle? or while accelerating or cruising)

[Jrosh1223]

Would the lower EGR being stuck open throw codes? The exhaust smells at idle and now while accelerating/cruising. We replaced the differential pressure hose before the DPF, and inspected the nearby hoses, so I'm somewhat doubtful this would be the cause of the issue. Could the issue be related to a gasket/clamp?

[wcs531]

So after googling the new codes you had these dont necessarily say "negative pressure", which is what I was going off of before.

4CF3 Exhaust back pressure signal, sensor, dynamically implausible
4D01 Exhaust backpressure sensor, signal too low, diesel particulate filter differential pressure too low
4D99 Particulate filter system, minimum differential pressure under shot after regeneration, particle filter flow resistance low Bank 1

From the NA BMW Diesel facebook group when searching 4D99:
The 4D99 DPF code is due to pressure drop being TOO LOW across DPF after regeneration, suggesting the DPF either has a large hole thru its filter matrix (unlikely, but possible), or there's an issue with an exhaust leak which is MUCH more common (ie DPF is not plugged up).

Definitely sounds like an exhaust leak if youre smelling exhaust all the time. My guess would be the EGR cooler (different from lower EGR) which cracks fairly often. Hopefully not a cracked exhaust manifold. There should be a number of exhaust leak threads to dig through

[Jrosh1223]

The way I have discerned negative pressure is based off of my Foxwell scanner. At idle, I am observing around -8 to -1 mbar, and while driving I can see values ranging from -20 to -80 mbar. When pressure testing the DPF, we confirmed that pressure from the DPF appears to be fine. Would having a cracked EGR cooler throw any codes? If codes aren't being thrown, is there any other way I could verify the issue? Thanks again for your time and assistance!

Originally Posted by wcs531

So after googling the new codes you had these dont necessarily say "negative pressure", which is what I was going off of before.

4CF3 Exhaust back pressure signal, sensor, dynamically implausible
4D01 Exhaust backpressure sensor, signal too low, diesel particulate filter differential pressure too low
4D99 Particulate filter system, minimum differential pressure under shot after regeneration, particle filter flow resistance low Bank 1

From the NA BMW Diesel facebook group when searching 4D99:
The 4D99 DPF code is due to pressure drop being TOO LOW across DPF after regeneration, suggesting the DPF either has a large hole thru its filter matrix (unlikely, but possible), or there's an issue with an exhaust leak which is MUCH more common (ie DPF is not plugged up).

Definitely sounds like an exhaust leak if youre smelling exhaust all the time. My guess would be the EGR cooler (different from lower EGR) which cracks fairly often. Hopefully not a cracked exhaust manifold. There should be a number of exhaust leak threads to dig through

[wcs531]

I'm not sure what codes would be present as I haven't dealt with the issue personally, I have just seen it come up a bunch on the forums.

I believe the upper egr cooler on the 335d is the same, or at least close enough. They seem to have a larger DIY community and sometimes have more info than here

https://www.e90post.com/forums/showthread.php?t=1532837

[Jrosh1223]

Car was dropped off at a local shop today. Advised them of the work I have already performed (DPF cleaning, exhaust pressure sensor replacement, and exhaust pressure hose replacement). I'll update the thread when I hear back.

[jonmuery]

Does anyone know what goes on the pipe with the blue silicone hose on it? This is a new down pipe from Speed Power Shop? I know on the original DPF there are two tubes that had coolant running to it, but now that will be looped out. Not sure if I missed a vacuum line?

[Jrosh1223]

So I got an update from the shop.
I was told that the issue was the differential pressure sensor. I’ll be picking the car up over the weekend, but I’m curious as to if the smell in the cabin will be resolved. I had already replaced the exhaust pressure sensor, but now I’m left wondering if maybe the differential pressure sensor/lines running to the sensor were leaking resulting in the smell in the cabin. According to the shop, the codes have not returned yet, but I intend on checking the pressure readings when I pick the car up.

Originally Posted by wcs531

I'm not sure what codes would be present as I haven't dealt with the issue personally, I have just seen it come up a bunch on the forums.

I believe the upper egr cooler on the 335d is the same, or at least close enough. They seem to have a larger DIY community and sometimes have more info than here

https://www.e90post.com/forums/showthread.php?t=1532837