# Exhaust backpressure codes after massive DPF regen



## aaroneous (Mar 19, 2016)

Made a ton of progress recently chasing DPF issues... found consistently low engine temps, replaced the thermostat and started getting regular regen cycles. Since there were no regens for quite a while since the thermostat failed quietly, I was at 60g of soot mass. Once regens started again, the soot mass dropped dramatically - I checked after a few weeks of driving and it is at 2g which means that the DPF is cleaning itself.

The problem I'm running into now is exhaust back pressure sensor codes (among others):


```
Fault Code: 004A27
Fault Explanation: Intelligent Battery Sensor (Layer DIBS1)
Fault Code: 004D03
Fault Explanation: Exhaust back pressure sensor
Fault Code: 004B81
Fault Explanation: Abgasrueckfuehrraten control, control deviation
Fault Code: 004D01
Fault Explanation: Exhaust back pressure sensor
Fault Code: 004D16
Fault Explanation: DeNOx system efficiency
Fault Code: 0049E1
Fault Explanation: Reductant active tank heater
```
My wife has said that she occasionally gets limp mode (I think related to 004B81 above) that lasts 30 sec - 2 min and then goes away. Usually leaving the grocery store or school parking lots, rarely during actual driving -- though it happened for the first time on the highway last week.

Backpressure readings are looking like this:









Is this likely a sensor issue or an actual physical blockage? Maybe an EGR issue in there as well? We've got emissions renewal coming up, and I'm pretty sure I'll need to have this sorted before then. Trying not to give up on this thing, but this has been 80k miles of chasing my tail (now at 140k miles). Hoping to squeeze a little more life out of it because otherwise it is in perfect condition.

Thanks so much for the help!


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## dzlbimmer (Jul 16, 2017)

aaroneous said:


> Made a ton of progress recently chasing DPF issues... found consistently low engine temps, replaced the thermostat and started getting regular regen cycles. Since there were no regens for quite a while since the thermostat failed quietly, I was at 60g of soot mass. Once regens started again, the soot mass dropped dramatically - I checked after a few weeks of driving and it is at 2g which means that the DPF is cleaning itself.
> 
> The problem I'm running into now is exhaust back pressure sensor codes (among others):
> 
> ...


 is your engine turned off where the graph hits 0?

Btw your 2g is just an estimation. Are your regeneration happening at exact intervals (200mi iirc)?


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## aaroneous (Mar 19, 2016)

dzlbimmer said:


> is your engine turned off where the graph hits 0?
> 
> Btw your 2g is just an estimation. Are your regeneration happening at exact intervals (200mi iirc)?


The engine is _not_ turned off when the graph shows zero, though other logged values (soot mass as an example) read zero in the same spots, so I would be inclined to think those values are a logging anomaly and not a sensor anomaly.

According to Carly, my average regernation interval is 294km (~180mi).


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## dzlbimmer (Jul 16, 2017)

aaroneous said:


> The engine is _not_ turned off when the graph shows zero, though other logged values (soot mass as an example) read zero in the same spots, so I would be inclined to think those values are a logging anomaly and not a sensor anomaly.
> 
> According to Carly, my average regernation interval is 294km (~180mi).


When my exhaust pressure line was clogged, I was regenerating at an exact set interval (plus monitor acceptance). Found this by disconnecting the exhaust pressure sensor at the hose-to-sensor connection, and apply vacuum to the soft line going to the hard line going to the manifold. I was able to clean it out alright, if it had been a stocked item, I probably would have just gotten a new one.


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## aaroneous (Mar 19, 2016)

dzlbimmer said:


> When my exhaust pressure line was clogged, I was regenerating at an exact set interval (plus monitor acceptance). Found this by disconnecting the exhaust pressure sensor at the hose-to-sensor connection, and apply vacuum to the soft line going to the hard line going to the manifold. I was able to clean it out alright, if it had been a stocked item, I probably would have just gotten a new one.


So this makes sense if the pressure line to the sensor is clogged -- i.e. the sensor reading is incorrectly NOT from a sensor malfunction. I will explore this but, just to educate myself a little more, if the sensor is reading accurately is the likely culprit for a physical blockage the DPF itself or something else in the line? If this is the case, is removal and cleaning usually sufficient or am I looking at replacement?


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## aaroneous (Mar 19, 2016)

dzlbimmer said:


> Btw your 2g is just an estimation.


While the 2g is just an estimation, the difference in power from the engine at 60g and 2g estimated soot mass is night and day. It went from hardly being able to get out of its own way to feeling like it actually has a turbo strapped to it. There is still a ton of lag, but I'm not expecting sports car acceleration out of it. Just trying to figure out what codes are symptoms and which is the cause...

I noticed this morning when my wife parked in the garage that there was a fairly significant oil spot under the passenger side of the engine, which makes me think the back pressure could be causing oil leaks in the turbo?

Really appreciate the input!


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## aaroneous (Mar 19, 2016)

Sorry to revive this one, but I still haven't gotten to a spot where I know how to remedy this. I'm feeling fairly confident that the readings are correct at the sensor because of the oil leak under the turbo... My hypothesis is that the high back pressure is being caused by a physical blockage and is pushing oil through seals in the turbo. If this is the case, is the only way to solve the blockage to replace the DPF or have others found success with cleaning? Are there any other likely culprits besides the DPF itself?


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## only6spd (Mar 30, 2016)

aaroneous said:


> Sorry to revive this one, but I still haven't gotten to a spot where I know how to remedy this. I'm feeling fairly confident that the readings are correct at the sensor because of the oil leak under the turbo... My hypothesis is that the high back pressure is being caused by a physical blockage and is pushing oil through seals in the turbo. If this is the case, is the only way to solve the blockage to replace the DPF or have others found success with cleaning? Are there any other likely culprits besides the DPF itself?


Did you ever get any of this sorted out?


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## Marti Mouse (Jul 25, 2020)

only6spd said:


> Did you ever get any of this sorted out?


If love an update to this!


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## Doug Huffman (Apr 25, 2015)

Marti Mouse said:


> If love an update to this!


@Aaroneous has not been back since the move to the new software and likely for some time before that.


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## Marti Mouse (Jul 25, 2020)

Doug Huffman said:


> @Aaroneous has not been back since the move to the new software and likely for some time before that.


Bummer. So much catching up to do.


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## Hayden9 (Oct 8, 2020)

My x5 does this, I was hell bent on it being the dpf I’m not thinking it’s a seal problem in the turbo due to excessive white smoke from oil filler even after replacing pcv


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## Marti Mouse (Jul 25, 2020)

Hayden9 said:


> My x5 does this, I was hell bent on it being the dpf I'm not thinking it's a seal problem in the turbo due to excessive white smoke from oil filler even after replacing pcv


I'm not getting any smoke. They should be done with the DPF cleaning today, so fingers crossed. Took it to a diesel place that specializes in DPF cleaning where they take it out, flush it for a while, then bake it at its regeneration temp, clean again and inspect, then reinstall if all looks good. If it doesn't look good will buy a new one and have them put it in. Supposedly my swirl flaps are all crudded up though, so that's the next project.


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## Hayden9 (Oct 8, 2020)

Marti Mouse said:


> I'm not getting any smoke. They should be done with the DPF cleaning today, so fingers crossed. Took it to a diesel place that specializes in DPF cleaning where they take it out, flush it for a while, then bake it at its regeneration temp, clean again and inspect, then reinstall if all looks good. If it doesn't look good will buy a new one and have them put it in. Supposedly my swirl flaps are all crudded up though, so that's the next project.


I really reckon it's something else causing the symptoms hey unless ur dpf light is on, which still likely could be something else I'm not wanting to change dpf because it'll likely happen again as soon as the dpf empties it fills right back up in 10 mins and does another regen yet ash level only 28g soot goes to 40 then regens


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## Marti Mouse (Jul 25, 2020)

Well my mechanic told me it was the DPF per ISTA.


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## badong3b (2 mo ago)

so the dpf cleaning works? for how many years? or months?


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## schoon.skyy48 (Oct 18, 2021)

badong3b said:


> so the dpf cleaning works? for how many years? or months?


 I just passed 2 years after my cleaning and i still have some EGR and vacuum leaks (plus a suspected VCG leak) causing problems, but the DPF itself seems fine.


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