[T6_measured] 01-Engine - Built-in test for EGR

[mmi]

So it seems - inevitable P0401.

Well, visited a VW garage to be tested - the van had accumulated 30 events in ECU's memory since July 2021 (since 20 months now). Eventually managed turn on the emission light at event number 31 - thus had a priviledge to have EGR flow tested. The result - pending - the ODIS went to an unending loop without a concluding result.

Meanwhile, I think I have reproduced the EGR flow test using VCDS. However, I don't have any reference value to estimate the degree of EGR cooler blockage. Neither did ODIS tell the reference value (should have told but the computer said no) - thus the final test is still pending.

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EDIT (20.9.2024):
The pass/fail threshold value is for air mass flow LOW/HIGH < 0.41. See here Egr fault P0401
The results in this thread were calculated for air mass HIGH/LOW thus pass value would be greater than 1/0.41 = 2.44

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Dear Forum members, I would appreciate if members equipped with VCDS could run the T6 engine's built-in test for EGR and post the result files here for future reference. I'm more than happy to provide the graphs in return. The more the merrier!

@Dellmassive - I'm intrigued to see how the new EGR performs!

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How to:​

General conditions​

• Download the attached measurement setup file TEST_EGR_DPF_FLOW.u01 - remove the .PDF extension so it will become a VCDS compatible .u01 file
  • Alternatively can also tick the parameters individually as on screen captures further down

• Proceed as below - preferably immediately after a (minimum of 15 minute) drive so everything is warmed up - for comparable results.
• Before coming to halt switch off Stop/Start and turn off AC .
• Let engine idle
• == Unfortunately can't proceed if DPF regeneration is in progress ==

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(1) Create engine blockmap data file​

• VCDS > Applications > Controller Channel Map >​

  • 
• Tick the boxes as above and click Go
• VCDS flashes screen for approx. two minutes. When finished click Done, Go Back

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(2) Run engine's built-in EGR flow test​

• VCDS > Select > Engine > Basic Settings
• Select - Show Measuring Data
• Spoiler: More

  
• Load measurement setup file TEST_EGR_DPF_FLOW.u01 (Load selection from file)
• Spoiler: More

  
  
• Spoiler: Now should look like this

  
• Click Log , enter file name
• Click Start (VERY IMPORTANT STEP!!)
• Select IDE00456-Checking exhaust gas recirculation (from pull-down menu if not shown)
• Click Go!
• Proceed as instructed on screen (Hold brake pedal and accelerator pedal) - test runs 60 seconds
• Spoiler: More

  
• When finished make a note of the message and let logging run for another 15 seconds
• Spoiler: More

  
• Stop (the data logging)
• Done, close
• Back out from Basic Settings, Close controller, etc. exit VCDS
• Switch off the engine, etc.

EDIT (2023-04-26) Added parameter IDE04090 Exhaust temperature bank 1 into measurement setup to capture DPF conditions more accurately. Thus the screenshots are slightly different. Could compensate the extra parameter by clicking on "Turbo" button.

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(3) Please post the logs (2 files)​

• The log files (2 of them) are in folder C:\Ross-Tech\VCDS\Logs\...
• The file Blockmap-01...CSV is a package of approx 1500 engine parameters - for further and possibly future evaluation of the test (e.g blockage vs. mileage vs. DPF ash accumulation)
  • Besides the above the collecting the above at (1) lets engine and exhaust temperatures stabilise so can be compared with others recorded similarly
• The actual log file LOG-01-.....CSV (or named by you) contains timestamped measured values.
• The particle filter air pressure sensor here is a kind of extra bit - a try to evaluate DPF condition as it's pressure loss is measured controlled way - though needs to be compared with soot and ash masses at the moment of testing (these are found in blockmap).

Thank you very much in advance!​

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Other related threads​

EDIT 17.3.2024:​

EGR valve test procedure - actual vs. requested EGR valve position​

Possibly related fault: P046C​

​

EGR Valve Self Test Procedure (IDE00242)- P046C?

So, I've been getting the all too common P046C fault code along with P2457 (Insufficient EGR Cooling Performance). Neither alone will flag a check engine light but combined they sometimes seem to. To try to figure out what is going on, I ran an EGR Flow test on VCDS using instruction from @mmi...

www.t6forum.com

 

[mmi]

An appetiser for now.
The result plots will be a scaled/syncronized combination of these now below separate graphs. Quite an interesting RPM pattern

 

[mmi]

EDIT: post added 18.5.2023.

"Thermal windows"​

VW note B0A6 - Transaction No.: 2067703/4​

According to the new judgements of the European Court of Justice (ECJ) it appears that the so-called “thermal windows” may no longer be permitted in certain areas.​

The thermal window describes the outside temperature-dependent regulation of the exhaust gas recirculation. ​

A solution is in preparation for the affected vehicles (T6). We will contact you as soon as it is available.​

​

Well, regarding the temperature-dependant EGR operation - monthly occurencies of P0401 faults (never dash warning light) plotted below - as well as monthly average temperatures in Finland.



Interestingly the winter months were fault free - actually the fault was never triggered below +14 °C (logged air intake temperatures at every fault).

 

[mmi]

EDIT: post added 18.5.2023

(1) RPM during the test - commanded by the ECU​

(2) EGR valve position during the test - cycles from 0% (no recirculation) to -65% (max recirc at the test)​

(3) Intake air flow during the test​

The maximum is full flow (no recirculation). Minimum shows EGR's capability to direct exhaust back to combustion - the less fresh air the better.

Also included calculated HIGH/LOW ratio - which presumably indicates how clogged the EGR cooler is.

(4) Pressure loss over DPF during the test​

Needs further evaluation and reference tests how to extract DPF condition from this. Anyways, the "standardised" value would be the maximum because the minimum is affected by EGR cooler blockage.

(5) Exhaust temperature during the test​

Average DPF temperature (S3, S4) during the test was 170 °C. The engine and exhaust were preheated by 30 km drive, engine was not stopped during preparations (VCDS hook-up) for the test. The DPF temperature affects siginificantly to pressure loss.

 

[Dellmassive]

Sure. I'll try and get some data for you tomorrow.

 

[Alied]

Hi @mmi I hope I've done it right?

 

[n10n]

2018 CXEB @72000km

 

[Alied]

Hi @mmi I hope I've done it right?

Forgot to say CFXA engine at 38000 miles 2017.

 

[Dellmassive]

2018
CXEB 204
63k miles
(NEW EGR/Cooler last month)


...


Blockmap & Log attached.


....


VCDS sign off after test:





+++++++++++


@mmi time for you to do your expert graphs and analysis.


.

 

[n10n]

2018 CXEB @72000km

The previous one was right on the verge of regen, so here's another one taken after it completed and some miles covered.

 

[mmi]

Hi @mmi I hope I've done it right?

Thank you very much. Attached the data plotted.

(1) RPM during the test​

(2) EGR valve position during the test - cycles from 0% (no recirculation) to -65% (max recirc at the test)​

The EGR normally runs both positive and negative values - yours was on positive side before the test.

(3) Intake air flow during the test​

The maximum is full flow (no recirculation). Minimum shows EGR's capability to direct exhaust back to combustion - the less fresh air the better.

Also included calculated HIGH/LOW ratio - which presumably indicates how clogged EGR cooler is. Higher the ratio the better. Mine is already down to 1.8 - assuming it's at the point needing attention because throwing P0401 code every now and then.


The values are averages of the highs and lows during the test.

(4) Pressure loss over DPF during the test​

Needs further evaluation and reference tests how to extract DPF condition from this. Anyways, the "standardised" value would be the maximum because the minimum is affected by EGR cooler blockage. Perhaps another measurement in 6-12 months?

 

[mmi]

2018 CXEB @72000km

Thank you very much. Plots below - both just before DPF regen and after.

Before DPF regen​

​

(1) RPM during the test​

​

​

(2) EGR valve position during the test - cycles from 0% (no recirculation) to -65% (max recirc at the test)​

​

​

(3) Intake air flow during the test​

​

​

(4) Pressure loss over DPF during the test​

​

​

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After DPF regen​

​

(1) RPM during the test​

​

Hmm... there is a 10 second gap in the data - from 53 to 63 seconds - one cycle lost

(2) EGR valve position during the test - cycles from 0% (no recirculation) to -65% (max recirc at the test)​

​

(3) Intake air flow during the test​

​

(4) Pressure loss over DPF during the test​

Is the EGR still the original one? Flushed?

 

[mmi]

2018
CXEB 204
63k miles
(NEW EGR/Cooler last month)

Thank you very much - the data from a new shiny EGR is definitely essential to evaluate condition of older ones

(1) RPM during the test​

​

​

(2) EGR valve position during the test - cycles from 0% (no recirculation) to -65% (max recirc at the test)​

​

(3) Intake air flow during the test​

The maximum is full flow (no recirculation). Minimum shows EGR's capability to direct exhaust back to combustion - the less fresh air the better.

Also included calculated HIGH/LOW ratio - which presumably indicates how clogged EGR cooler is. Higher the ratio the better. Mine is already down to 1.8 - assuming it's at the point needing attention because throwing P0401 code every now and then.

​

The values above are averages of the highs and lows during the test.

(4) Pressure loss over DPF during the test​

 

[n10n]

Thanks, something to think about!

Hmm... there is a 10 second gap in the data - from 53 to 63 seconds - one cycle lost

Most likely the data quality issues would be attributable to my crappy 4g wifi router, I used Hex-Net over wifi… good to know, will use cable next time

Is the EGR still the original one? Flushed?

Original EGR and not flushed as far as I know, and I’ve owned the vehicle for 42000km.

 

[n10n]

Original EGR and not flushed as far as I know, and I’ve owned the vehicle for 42000km.

I do >90% motorways / b-roads and minimal urban or city driving. Also I use additives, Redline RL-2 as most recently with every filling. The intention has been to keep injectors clean mostly and I don’t know if it has anything to do with the apparent good EGR condition… this is not an advertisement. Overall I tend to not drive sparingly but honestly smashing down motorways 90% of time I don’t think the driving style matters much in the remaining 10%.

As for why I posted after regen I took a cursory peek on the data before graphed out and noticed the DPF pressure was high in my first sample, probably indicative of DPF resisting the flow more right before regen - thought this might be interesting.

Before:


After:

 

[mmi]

As for why I posted after regen I took a cursory peek on the data before graphed out and noticed the DPF pressure was high in my first sample, probably indicative of DPF resisting the flow more right before regen - thought this might be interesting.

Well spotted - and thanks for sharing.

I seem to have created a habit recording almost the same as above at different phases of DPF regen cycle by letting engine idle 15 seconds before switching off. I do see similar behaviour - more soot, higher pressure. However, DPF temperature seems to play very significant role in DPF pressure loss (hot DPF = more pressure loss) - thus also those need to be accounted for.

Anyways, just edited the "instructions" and replaced the VCDS .u01-file with another one which will now record also DPF input and output temperatures - parameter IDE04090 Exhaust temperature bank 1 - actually will record all four exhaust temperature sensors. Let's see how it pans out.

I think we could use this setup also to verify DPF pressure sensor data validity as the ratio of pressure high/low is quite close to air flow high/low ratio

 

[n10n]

I think we could use this setup also to verify DPF pressure sensor data validity as the ratio of pressure high/low is quite close to air flow high/low ratio

Nice idea, I like it!

As you say at the very least might help out in differentiating partial sensor failures from real blockages / leaks

 

[n10n]

However, DPF temperature seems to play very significant role in DPF pressure loss (hot DPF = more pressure loss) - thus also those need to be accounted for.

Just a shower thought but I wonder if the temperature effect could be approximated by the ideal gas law? Like, if in two different measurements the volume is equal but temperature is higher in one of them, the pressure must also be higher.

 

[mmi]

Posts #3 and #4 updated with new data.

Dear Forum - data contributions welcome!

 

[n10n]

"Thermal windows"​

VW note B0A6 - Transaction No.: 2067703/4​

According to the new judgements of the European Court of Justice (ECJ) it appears that the so-called “thermal windows” may no longer be permitted in certain areas.​

The thermal window describes the outside temperature-dependent regulation of the exhaust gas recirculation. ​

A solution is in preparation for the affected vehicles (T6). We will contact you as soon as it is available.​

European Court of Justice confirms: Thermal windows are illegal defeat devices — Dieselgate Experts Dieselgate Experts in Baltics | Klauberg Dieselgate | Dieselgate in Latvia | Dieselgate in Finland | Dieselgate in Lithuania

Hundreds of thousands of vehicles in Europe are affected. With a bang, the ECJ opens up legal protection and legal action options for many thousands Mercedes, BMW and Opel buyers that include so-called thermal windows. This refers to software that switches off the exhaust gas purification system

dieselgate.legal

"The ECJ has now ruled (Case C-134/29): Thermal windows are not permitted under European law and are therefore illegal. The use of the window violates European environmental regulations with regard to newly registered motor vehicles."

Remains to be seen but maybe concerns new vehicles only. I wonder what the effect would be if the removal of thermal windows was forced upon existing vehicles through a recall and/or checked in MOT.