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Discussion Starter #1 (Edited)
Hi guys
My 2011 (2010) V6 TDI 7P5 Treg is showing off it''s orange engine warning light with the EGR P0401 Insufficiant flow error.

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Address 01: Engine (J623-CASA) Labels:. 059-907-401-V2.clb
Part No SW: 7P0 907 401 HW: 7P0 907 401
Component: 3.0TDI EDC17 H17 0011
Revision: 51H17---
Coding: 292A401A237E01020000
Shop #: WSC 35618 001 1048576
ASAM Dataset: EV_ECM30TDI0117P0907401 002013
ROD: EV_ECM30TDI_VW52.rod
VCID: 6CD64C99873E1224EB-8038

1 Fault Found:
4807 - EGR System
P0401 00 [096] - Insufficient Flow
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 155500 km
Date: 2019.07.20
Time: 11:00:20

Engine speed: 1734.50 /min
Normed load value: 59.2 %
Vehicle speed: 50 km/h
Coolant temperature: 75 °C
Intake air temperature: 27 °C
Ambient air pressure: 990 mbar
Voltage terminal 30: 13.540 V
Unlearning counter according OBD: 39
Mean injection quantity: 22.24 mg/stroke
Control Module temperature: 29.6 °C
EGR_governor_deviation: -187.1 mg/stroke
Inj Ctl q Curr: 22.39 mg/stroke
Mass_air_flow_sensor_drift: 1.2413
Air_Flow_Rate_from_Mass_Air_Flow_Sensor_kg_h: 184.8 kg/h
Actual charge pressure: 1413 hPa

Readiness: 0 0 0 0 0
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So far I've replaced the the EGR with a brand new one , Pierburg (the old one didn't look too bad though), cleaned the EGR pipe to the intake manifold (good flow), cleaned the small gap in the bottom of manifold that actually brings in the air from the EGR pipe (crazy placement, built for clogging.!), cleaned the intake valve. I also tried the EGR cleaning fluids (diesel additive), and also did the wallpaper steamer trick.

Looking at the error above I see the the EGR_governor_deviation: -187.1 mg/stroke is kind of closing of the Air_Flow_Rate_from_Mass_Air_Flow_Sensor_kg_h: 184.8 kg/h

I'm getting ready to rip off and clean the whole manifold with blow torch and pressurised air, but after the cleaning I've done the car feels so much better and much more "snappier" than before.

Do anyone of you know how to interpret the error above? It seems to me that maybe something else might be wrong? Something that prevents EGR totally? Faulty EGR censor? Vacuum?

I'd appreciate any guidance for more troubleshooting here. Should I check more around vacuum? Any other censors? I clear the code, but it keeps coming back pretty often now.

Getting a bit frustrated now ](*,)

Here's a video of a VCDS monitoring session:
 

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EGR flow is detected by the ECU using the MAF and MAP sensors. If any of them is bad, the ECU might detect a lack of EGR flow, despite there being a sufficient one. It might be worth checking whether these sensors deliver correct data.

Also try running an EGR adaptation in ECU > Basic settings first!
 

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Discussion Starter #3
EGR flow is detected by the ECU using the MAF and MAP sensors. If any of them is bad, the ECU might detect a lack of EGR flow, despite there being a sufficient one. It might be worth checking whether these sensors deliver correct data.

Also try running an EGR adaptation in ECU > Basic settings first!
Thanx, Gnits ?
I did run an EGR test with basic settings. Values didn't change much, so might be a good idea with adaption.
Should I set it to 33768?

Also, regarding the sensors; where are they all located? The MAF is just by the air filter, but where are the other ones?
 

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Thanx, Gnits ?
I did run an EGR test with basic settings. Values didn't change much, so might be a good idea with adaption.
Should I set it to 33768?
No, the adaptation I'm talking about is the test you've run. Whenever the EGR is replaced or cleaned you're supposed to run that, so that the ECU can learn the new limit/behavior of the valve. The test should also show if there is some problem with the detection of the EGR flow or the intake air mass measurement.

Also, regarding the sensors; where are they all located? The MAF is just by the air filter, but where are the other ones?
MAF is right after the air filter on the intake hose. MAP sensor is between the intercooler and the shut-off / EGR valve on the charge air hose.
 

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Discussion Starter #5
Thanx a bunch!
Then I suspect the MAP might be the culprit here. I'll try to locate it in there. Is it directly mounted in the manifold, or is it connected with tubes?
 

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The test should also show if there is some problem with the detection of the EGR flow or the intake air mass measurement.
Btw, regarding the EGR test, how will it show if there's a problem? I can run the test again while recording the screen, and maybe you can see if there's any issues? Any specific params I should show?

Sent fra min CLT-L29 via Tapatalk
 

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Btw, regarding the EGR test, how will it show if there's a problem?
Depends on the problem you might have. The EGR flap position might not read the specified/expected values. The fresh air intake mass might not change as expected (it should be a lot less when the EGR is open, because then the EGR is providing large part of the "air" for the inlet). These will be described either in the test's description box or in the hint popups that show in VCDS when you click in one of the MVB fields on the test screen.

I can run the test again while recording the screen, and maybe you can see if there's any issues? Any specific params I should show?
The built-in adaptation test will always show a pre-determined set of measuring blocks, and you can't change that.
 

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Is this the one? See pic. Seems pretty hard to get out.
No, this is a vacuum solenoid switch valve. Maybe for the EGR valve or EGR cooler valve, or for the turbo. I'm not familiar with that particular engine.

A MAP sensor, however, looks generally like this (even though it might vary by engine and design) and plugs into a very thick hose (charge air hose), or into the intake manifold itself:

 

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Think I located it see pic. Just before the control valve. Could the reason for this be a faulty control valve (4E0145950H). Is it possible to test it with vcds with the throttle body test (even if it's tdi)


Sent fra min CLT-L29 via Tapatalk
 

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Think I located it see pic.
Yes, that's it. With "0 281 002 401" number on it.

Could the reason for this be a faulty control valve (4E0145950H).
No, but it could be faulty on its own, and that might confuse the ECU, which could then trip a false code.

Is it possible to test it with vcds with the throttle body test (even if it's tdi)
Test the MAP sensor? To a certain degree, yes, with the turbo adaptation in the basic settings, Group 011. More important would be testing the MAF first though.

Is it possible to test it with vcds with the throttle body test (even if it's tdi)
No, TDIs only have shut-off flaps, no throttle bodies. And I have not seen there being a test/adaptation available for those units in VCDS anyway. Even if there would be, I don't know how that could be useful in diagnosing either MAP or EGR problems.
 

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Discussion Starter #14
Thanx again, Gnits ? You're really helpful!
I meant testing the shut off flap based on the location of the MAP sensor.
I did the EGR cooler shut switch flap test, and that also seems OK. Opening and closing.
I'll get hold of some sec torx to check / clean the MAP.
 

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Discussion Starter #15
Latest update: I haven't been able to work on the car for a few days, however after the the last EGR adaption (and partial DPF regeneration forced) the engine lights has not come up. Scan don't show P0401 either.
I'm going on a trip with heavy trailer later today (horse trailer), and that will most certainly bring it out if it's still there.

I'm also considering running DPF cleaner and other cleaners through the whole system.

Thanx so far for helping me out here! If anyone needs any tips for replacing EGR valve (not cooler yet) on this baby I'll be happy to help :)
 

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Discussion Starter #16
Ok, so it's back again..
Gnits, do you have any idea what the flow should be on this engine on different RPM's / load? The "normal" flow?

I'm really suspecting a clogged EGR cooler here too.

/D
 

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Gnits, do you have any idea what the flow should be on this engine on different RPM's / load? The "normal" flow?
No, and that's the prerogative of the ECU, ie. to determine how much EGR flow it allows at specific RPM/load/speed/temperature/etc. conditions. All you need to know is that you should have several mg/s less fresh air taken in (as measured by the MAF sensor) when the EGR valve is fully open, than when it's closed. How much less depends on the engine, and you'll find instructions regarding that on the VCDS EGR adaptation screen in the description.
 

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Discussion Starter #18
No, and that's the prerogative of the ECU, ie. to determine how much EGR flow it allows at specific RPM/load/speed/temperature/etc. conditions. All you need to know is that you should have several mg/s less fresh air taken in (as measured by the MAF sensor) when the EGR valve is fully open, than when it's closed. How much less depends on the engine, and you'll find instructions regarding that on the VCDS EGR adaptation screen in the description.
Thanx again. Yep, the MAF reports lower flow when EGR is open, but I guess it's not low enough for the ECU to be happy. As I have already cleaned out EGR pipe, replaced EGR valve and checked many of the other, big tubes I suspect EGR cooler to be the reason for this. These issues are quite common up here in the north. Replacing EGR cooler is a massive job.
I could also try cleaning the intake manifold as it seems to be an easier job, actually. I'll keep this thread updated as I dig more.
 

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Guys, any update on this topic? My Touareg (2011) V8 TDI seems to have the same issue. I have replaced both EGR valves and the code EGR P0401 still pops up. Actually before this code appeared I have replaced MAF sensors, but not sure if this can be anyhow connected.
 
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