meerschm
Top Post Dawg
- Joined
- Apr 18, 2009
- Location
- Fairfax county VA
- TDI
- 2009 Jetta wagon DSG 08/08 205k buyback 1/8/18; replaced with 2017 Golf Wagon 4mo 1.8l CXBB
Managing a sooty tailpipe Waiting for P0401
Updated several times in 2016 and 2017.
2009 to 2014 TDI Diesel Particulate Filters (DPF) have been identified as sometimes cracking, which allows soot to bypass the filter. When this happens and soot enters and fills up the low pressure exhaust gas recirculate (EGR) filter, which will cause a P0401 error to be logged. VW has issued a TSB which describes checks for soot in the EGR filter upon a P0401 error. The TSB states that P0401 error, and soot in the connection between DPF and LP EGR filter calls for replacement of the DPF and EGR filter.
part of the TSB:
The P0401 may also be caused by high pressure EGR issues, but soot in the tailpipe is a good sign the issue is low pressure EGR.
Below is the result inside the low pressure EGR filter. the screen becomes covered in soot which comes through a damaged DPF.
http://forums.tdiclub.com/showpost.php?p=5136097&postcount=241 (photo credit)
The Diesel Particulate Filter (DPF) is the only component in the exhaust treatment capable of blocking soot. If there is any soot in the end of the tailpipe, it follows that soot would also be noted at the input to the Low Pressure EGR filter as referenced in the TSB.
Further isolation of a P0401 error can be done by running Basic settings. (003, 067, 078) (on the engine controller, using VCDS)
http://www.ross-tech.com/vcds/tour/b-settings.php
These errors may start intermittently, and a VCDS scan will show the recorded errors. The engine controller can be checked for errors using VCDS. the error log includes freeze frame data recorded when the error is noted. As additional errors are noted, the information is updated, including a count (frequency). These errors are also noted and reported by the OBD-II functions. VCDS will let you read these as well.
http://www.ross-tech.com/vcds/tour/obd-2.html
When a P0401 error occurs, it also can be seen in the OBD as a pending code. if the next time the check is run, the code repeats, it is recorded as a current DTC, and the MIL (Malfunction Indicator Lamp, aka check engine) is lit up, notifying the driver that there is a problem. The OBD readiness screen will note the recorded error, and if the MIL is on or not. It is not unusual for these errors to begin once in a while, and for the MIL to go away on its own, after some driving.
Always a good idea to follow up any MIL to find out what caused it. Most errors stay recorded for reference, even if the MIL goes out
Properly functioning, intact DPF will capture all the soot, and the tailpipe will be clean. There a few of us who have tailpipes which are not so clean, and a wipe with a paper towel reveals black soot.
I have a tailpipe that is a little sooty, but started with no P0401 errors recorded. I have procured a used replacement DOC/DPF, NOX cat, and egr filter, but want to wait to see if it will be needed. After I picked these up, the whole tdi emissions cheat came up, I may only have a spare DOC/DPF, since the anticipated "fix" seems to include a new design NOX cat, EGR filter, and exhaust flap. since my 2009 DPF is part of the same unit with the NOX cat, my hope is that the "fix" will include a DOC/DPF.
Seems like I put over 40,000 miles on my car between first noting some soot and seeing the first P0401 error. As of May 2016, I had over 30,000 miles with some soot in the pipe, but no errors. Life is good.
October 2016, just went over 180,000 miles, so call it 40,000 miles with some crackage in my DPF, and occasional P0401 errors.
April 2017, went over 200,000 miles on the car. MIL comes and goes (P0401). still able to clear codes and drive to get a clear emissions screen.
I am looking for history from other cars of clean or sooty tailpipes, including mileage of observed conditions.
My goal in starting this post was to see if there is other info which can be used to predict how long one could drive with a slightly sooty tailpipe, before having trouble passing emissions inspection. With some help from other TDIclub members, was able to find a path through the fog and understand how Basic settings data can provide insight into how the car systems are working, and narrow in on what separates conditions that throw a P0401 error from those which do not.
Fault codes (including the P0401) can be obtained via VCDS auto-scan http://www.ross-tech.com/vcds/tour/main_screen.html
or from the fault code screen which is available in the engine controller screen.
http://forums.tdiclub.com/showpost.php?p=4871094&postcount=19 describes basic settings EGR check (basic settings 003 is the high pressure EGR. HP EGR issues can also cause the P0401 error, but are not related to a cracked DPF or LP EGR).
http://forums.tdiclub.com/showpost.php?p=4895896&postcount=64 Matt shared a couple checksheets related to DPF health
Basic Settings 67 will exercise the Low Pressure EGR valve. this is available on the VCDS pull down list.
Basic Settings 78 will increase idle speed for a read of the LP EGR pressure. It is not on the pull down, but you can enter 78 in the Basic settings screen.
VCDS and the controller inside the car will only run a single basic setting at a time; you have to back out of basic settings and then come back to run another one.
Here is a plot of collected data from Basic settings 78 on several cars. (PM me if you want a copy of the spreadsheet with all the data)
I used excel to create a spreadsheet populated with data collected from my car and from other members who shared data from their cars. Figures below are from excel, with some image manipulation to add notes and lines, where I thought they were helpful.
Data point colors identify a specific car. Guess is that readings to the right of the diagonal line indicate too much pressure across the low pressure EGR filter, and likely MIL (check engine light) illuminated, and P0401 error from cracked DPF. Readings to the left of that line seem ok. Close to the line, and you might get an error logged once in a while without the MIL.
More details related to this chart http://forums.tdiclub.com/showpost.php?p=5007471&postcount=195
2016/09/21 update: based on my recent data, the good/bad line in the above figure is a bit more to the right, something like 120mbar at 200 degrees.
2016/11/21 update: next figure shows data from November. I now have been watching the P0401 error come and go on my car, and see a little more clearly where the line is between acceptable egr pressure and pressure high enough to cause the P0401 error. It is difficult to exactly match a P0401 error (which is captured while in motion) with Basic settings 78 data (which can only run with the car in park). But I can identify the data with recent updates to the P0401 error freeze frame data, or lack of increments. Seems no way to record tests of whatever throws the P0401 when it does not register the error, but this results in the dropping of a "pending" OBD code.
Data points to the lower right of my hand drawn line in the figure below are captured shortly after an increase in the "frequency" value logged P0401 error, and when the OBD shows a pending code. I saw the MIL come on for part of a road trip to Michigan, but it was extinguished by the time I hooked up the VCDS.
This chart includes BS 78 data from my car, during the full month of November 2016.
Points colored red are close to failed computer checks that log a P0401 error (or increase the P0401 error 'frequency' count)
Numbers close to data points are the day of the month the data was logged. (note that the month started and ended with BS 78 checks far into the "good" range)
If you would like to add data to this discussion, some info which could help follow (ok to post as much or as little as you like):
1/15/16. updated this post to reflect a little more learned. this is very much a learn on the way kind of discussion, with a few stops along the way for side discussions..
2/14/2016 added basic settings 78 chart, and TSB section.
5/7/2016 update. my pipe is still a little sooty, but no P0401 errors. couple weeks ago, passed VA pre-registration emissions check.
9/17/2016 update. Earlier this month I was greeted with an MIL, and the P0401 error. cleared codes and watched them come back. I logged quite a few entries and data, and verified that P0401 errors can build up in the engine controller without getting more than an occasional pending code in the OBD emissions reporting. As of today, I see 8 instances of the P0401 code logged since I reset the codes 9 days ago (includes a turnpike/freeway drive from MI to VA and a weeks worth of ten mile commutes) no pending emission codes or failures which would prevent passing obd emissions inspection. since the reset, there are several times which checks revealed pending emissions codes and the P0401.
4/8/2017 update: went over 200,000 miles. still watching the error come and go, while waiting for the emissions "fix" from VW.
Updated several times in 2016 and 2017.
2009 to 2014 TDI Diesel Particulate Filters (DPF) have been identified as sometimes cracking, which allows soot to bypass the filter. When this happens and soot enters and fills up the low pressure exhaust gas recirculate (EGR) filter, which will cause a P0401 error to be logged. VW has issued a TSB which describes checks for soot in the EGR filter upon a P0401 error. The TSB states that P0401 error, and soot in the connection between DPF and LP EGR filter calls for replacement of the DPF and EGR filter.
part of the TSB:
Below is the result inside the low pressure EGR filter. the screen becomes covered in soot which comes through a damaged DPF.
http://forums.tdiclub.com/showpost.php?p=5136097&postcount=241 (photo credit)
The Diesel Particulate Filter (DPF) is the only component in the exhaust treatment capable of blocking soot. If there is any soot in the end of the tailpipe, it follows that soot would also be noted at the input to the Low Pressure EGR filter as referenced in the TSB.
Further isolation of a P0401 error can be done by running Basic settings. (003, 067, 078) (on the engine controller, using VCDS)
http://www.ross-tech.com/vcds/tour/b-settings.php
These errors may start intermittently, and a VCDS scan will show the recorded errors. The engine controller can be checked for errors using VCDS. the error log includes freeze frame data recorded when the error is noted. As additional errors are noted, the information is updated, including a count (frequency). These errors are also noted and reported by the OBD-II functions. VCDS will let you read these as well.
http://www.ross-tech.com/vcds/tour/obd-2.html
When a P0401 error occurs, it also can be seen in the OBD as a pending code. if the next time the check is run, the code repeats, it is recorded as a current DTC, and the MIL (Malfunction Indicator Lamp, aka check engine) is lit up, notifying the driver that there is a problem. The OBD readiness screen will note the recorded error, and if the MIL is on or not. It is not unusual for these errors to begin once in a while, and for the MIL to go away on its own, after some driving.
Always a good idea to follow up any MIL to find out what caused it. Most errors stay recorded for reference, even if the MIL goes out
Properly functioning, intact DPF will capture all the soot, and the tailpipe will be clean. There a few of us who have tailpipes which are not so clean, and a wipe with a paper towel reveals black soot.
I have a tailpipe that is a little sooty, but started with no P0401 errors recorded. I have procured a used replacement DOC/DPF, NOX cat, and egr filter, but want to wait to see if it will be needed. After I picked these up, the whole tdi emissions cheat came up, I may only have a spare DOC/DPF, since the anticipated "fix" seems to include a new design NOX cat, EGR filter, and exhaust flap. since my 2009 DPF is part of the same unit with the NOX cat, my hope is that the "fix" will include a DOC/DPF.
Seems like I put over 40,000 miles on my car between first noting some soot and seeing the first P0401 error. As of May 2016, I had over 30,000 miles with some soot in the pipe, but no errors. Life is good.
October 2016, just went over 180,000 miles, so call it 40,000 miles with some crackage in my DPF, and occasional P0401 errors.
April 2017, went over 200,000 miles on the car. MIL comes and goes (P0401). still able to clear codes and drive to get a clear emissions screen.
I am looking for history from other cars of clean or sooty tailpipes, including mileage of observed conditions.
My goal in starting this post was to see if there is other info which can be used to predict how long one could drive with a slightly sooty tailpipe, before having trouble passing emissions inspection. With some help from other TDIclub members, was able to find a path through the fog and understand how Basic settings data can provide insight into how the car systems are working, and narrow in on what separates conditions that throw a P0401 error from those which do not.
Fault codes (including the P0401) can be obtained via VCDS auto-scan http://www.ross-tech.com/vcds/tour/main_screen.html
or from the fault code screen which is available in the engine controller screen.
http://forums.tdiclub.com/showpost.php?p=4871094&postcount=19 describes basic settings EGR check (basic settings 003 is the high pressure EGR. HP EGR issues can also cause the P0401 error, but are not related to a cracked DPF or LP EGR).
http://forums.tdiclub.com/showpost.php?p=4895896&postcount=64 Matt shared a couple checksheets related to DPF health
Basic Settings 67 will exercise the Low Pressure EGR valve. this is available on the VCDS pull down list.
Basic Settings 78 will increase idle speed for a read of the LP EGR pressure. It is not on the pull down, but you can enter 78 in the Basic settings screen.
VCDS and the controller inside the car will only run a single basic setting at a time; you have to back out of basic settings and then come back to run another one.
Here is a plot of collected data from Basic settings 78 on several cars. (PM me if you want a copy of the spreadsheet with all the data)
I used excel to create a spreadsheet populated with data collected from my car and from other members who shared data from their cars. Figures below are from excel, with some image manipulation to add notes and lines, where I thought they were helpful.
Data point colors identify a specific car. Guess is that readings to the right of the diagonal line indicate too much pressure across the low pressure EGR filter, and likely MIL (check engine light) illuminated, and P0401 error from cracked DPF. Readings to the left of that line seem ok. Close to the line, and you might get an error logged once in a while without the MIL.
More details related to this chart http://forums.tdiclub.com/showpost.php?p=5007471&postcount=195
2016/09/21 update: based on my recent data, the good/bad line in the above figure is a bit more to the right, something like 120mbar at 200 degrees.
2016/11/21 update: next figure shows data from November. I now have been watching the P0401 error come and go on my car, and see a little more clearly where the line is between acceptable egr pressure and pressure high enough to cause the P0401 error. It is difficult to exactly match a P0401 error (which is captured while in motion) with Basic settings 78 data (which can only run with the car in park). But I can identify the data with recent updates to the P0401 error freeze frame data, or lack of increments. Seems no way to record tests of whatever throws the P0401 when it does not register the error, but this results in the dropping of a "pending" OBD code.
Data points to the lower right of my hand drawn line in the figure below are captured shortly after an increase in the "frequency" value logged P0401 error, and when the OBD shows a pending code. I saw the MIL come on for part of a road trip to Michigan, but it was extinguished by the time I hooked up the VCDS.
This chart includes BS 78 data from my car, during the full month of November 2016.
Points colored red are close to failed computer checks that log a P0401 error (or increase the P0401 error 'frequency' count)
Numbers close to data points are the day of the month the data was logged. (note that the month started and ended with BS 78 checks far into the "good" range)
If you would like to add data to this discussion, some info which could help follow (ok to post as much or as little as you like):
Model year of your car:
Tailpipe condition: [clean, little soot, massive soot]
Odometer miles:
Codes recorded: [P0401, other?]
MIL?: [yes, no]
Basic settings 003 High pressure EGR Valve:
EGR Spec OFF/99% duty cycle/EGR (actual): [value in mg/str]
EGR Spec ON/60% duty cycle/EGR (actual): [value in mg/str]
OFF - On: [difference in mg/str]
Basic settings 067 Low pressure EGR valve:
On/40%: [value in mg/str]
Off/100%: [value in mg/str]
Off - On : [difference in mg/str]
Basic settings 078 (low pressure EGR) as the others, press on/off/next and note increased RPM
78-1 mbar:
78-2 %?:
78-3 mbar(offset):
78-4 Degrees C:
9/21/15 *******************NOTE: skip to post #54 or later before any data collection. the 03 measuring block collected in the EGR basic settings is high pressure EGR, not the Low pressure which is prone to clogging from a clogged DPF.Tailpipe condition: [clean, little soot, massive soot]
Odometer miles:
Codes recorded: [P0401, other?]
MIL?: [yes, no]
Basic settings 003 High pressure EGR Valve:
EGR Spec OFF/99% duty cycle/EGR (actual): [value in mg/str]
EGR Spec ON/60% duty cycle/EGR (actual): [value in mg/str]
OFF - On: [difference in mg/str]
Basic settings 067 Low pressure EGR valve:
On/40%: [value in mg/str]
Off/100%: [value in mg/str]
Off - On : [difference in mg/str]
Basic settings 078 (low pressure EGR) as the others, press on/off/next and note increased RPM
78-1 mbar:
78-2 %?:
78-3 mbar(offset):
78-4 Degrees C:
1/15/16. updated this post to reflect a little more learned. this is very much a learn on the way kind of discussion, with a few stops along the way for side discussions..
2/14/2016 added basic settings 78 chart, and TSB section.
5/7/2016 update. my pipe is still a little sooty, but no P0401 errors. couple weeks ago, passed VA pre-registration emissions check.
9/17/2016 update. Earlier this month I was greeted with an MIL, and the P0401 error. cleared codes and watched them come back. I logged quite a few entries and data, and verified that P0401 errors can build up in the engine controller without getting more than an occasional pending code in the OBD emissions reporting. As of today, I see 8 instances of the P0401 code logged since I reset the codes 9 days ago (includes a turnpike/freeway drive from MI to VA and a weeks worth of ten mile commutes) no pending emission codes or failures which would prevent passing obd emissions inspection. since the reset, there are several times which checks revealed pending emissions codes and the P0401.
4/8/2017 update: went over 200,000 miles. still watching the error come and go, while waiting for the emissions "fix" from VW.
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