Is my DPF finished?

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caller100
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Joined: Mon Mar 08, 2021 10:13 pm

Is my DPF finished?

Post by caller100 » Tue Mar 16, 2021 2:18 pm

Hi guys.

Firstly what a great app this VAG DPF is. It has enabled me to monitor my DPF on my Skoda Octy VRS MK3.

OK, so i have been monitoring the DPF over the last few months, and i noticed that now a regeneration occurs every 30-50km, it used to be around 100km before. And yes i do a lot of short journeys in the car.

When i see that the DPF is full (image1), i take the car on the motorway for a good run and it cleans the DPF (image2), which is great.

Looking at image1.png
The DPF is full at 100% + 5%
Soot Mass Calc (g) is at 24.63
The Oil Ash Residue is at 8.2 and 10%

Looking at image2.png
DPF at 16%
Soot Mass Calc (g) is at 3.70
The Oil Ash Residue is at 8.2 and 10%

I am struggling to make sense of these readings.

My question is - Is my DPF finished because of the Oil Ash Residue value? Do i need a DPF refurbishment or clean or replacement?

One other thing i noticed is that when i look at the DPF percentage at the start of my driving, it shows say for example 20% full, during my driving it only moves up 1% or 2%, but then 10 minutes later jumps to 100%. Does this mean that there could be some other problem causing this and is not the DPF??

I am worried that it may be some other problem causing the DPF to fill up, like the EGR valve or some carbon blockage?

Any help would be greatly appreciated.

Thanks

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admin
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Re: Is my DPF finished?

Post by admin » Tue Mar 16, 2021 6:25 pm

I don't see the attached images, but I can understand reading your message.

Oil ash residue is not a parameter strictly related to the regeneration process, it shows the amount of unburned oil ash that can't be removed by the filter because it doesn't burn during the regeneration. This value increases almost linearly with the mileage and it correspond to the life of the filter, in fact when it reaches the maximum acceptable value (set by VW engineers), the filter should be replaced because its performances are too much reduced. I write "should" because you can also drive with the oil ash over the maximum, but in this case it would be normal to have frequent regenerations.

To start and to stop the regeneration, the ECU uses only the soot mass calculated value (sometimes also the measured value in case of failure). Consider that the process usually stops when the soot mass is between 2 and 8 grams depending on the driving conditions.

The sudden increase of the soot mass calculated can be due to 2 possible causes (based on my personal experience):
  • you've reached the maximum distance or time between regenerations; the ECU has these 2 limits as a sort of protection against sensors failures
  • the DPF system has a sensor faulty; the most probable cause in this case a differential pressure sensor failure, usually changing this sensor solves the problem, but you need to do a deep diagnostic analysis to be have a confirmation
30-50km between regenerations is a very low value, I can suggest to ask for a check to a service.

caller100
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Joined: Mon Mar 08, 2021 10:13 pm

Re: Is my DPF finished?

Post by caller100 » Tue Mar 16, 2021 9:52 pm

Hello Admin.

Thank you for your reply.

I have now attached the two images - image1.png + image2.png

You mentioned the differential pressure sensor failure, do you mean the DPF pressure sensor? If so, i have already had this changed and come to think of it, the DPF started to fill up a lot quicker soon after.

If it is not the DPF pressure sensor, then could it be the EGR or something like this?

My Oil Ash residue is 8.2 and 10%, i saw somewhere that if the 10% gets to 40% then the DPF is finished? Is this correct?

What is the maximum acceptable Oil Ash Residue value?

I want to be certain that i have explored all other options before i take the decision to refurbish/clean or buy a new DPF.

Once again, thanks for your valuable input.

Cheers

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admin
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Re: Is my DPF finished?

Post by admin » Wed Mar 17, 2021 8:51 am

I still don't see any image ...

The oil ash percentage is the value you have to consider to check the DPF life. When i reaches the 100%, the DPF should be replaced, as the VAG engineers planned.

The differential pressure sensor is probably what you've replaced, I don't think there is a single "pressure sensor" in the DPF system.
And I think it's normal that your regenerations become more frequent after the replacement, because it the work was done well, all the learned parameters have been erased and not the ECU is learning them again but using a conservative approach.

It's not so easy to understand what's the problem using VAG DPF app, it would be better to check the engine with service diagnostic software.
With my app you could see it there's something not working as expected, like regeneration too much frequent or sudden values changing never happened in the past.

When your regeneration starts, what are the "time since last regen" and "distance since last regen" values?

Have you saved a log of your trips?

caller100
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Re: Is my DPF finished?

Post by caller100 » Fri Mar 19, 2021 4:40 pm

Hello Admin.

OK, so this time i decided to properly capture the DPF behaviour during my driving.

I will reference each screenshot i took during my stop/start driving with the time and parameters :

Time 17:55
The DPF capacity = 25% (dpf running at normal level)
Soot Mass Calc (g) = 6.08
Distance Since Last Regen. (km) = 5
Time Since Last Regen. (min) = 17
The Oil Ash Residue = 8.4 and 11%

Time 18:55
The DPF capacity = 32% (the dpf is turning pink colour)
Soot Mass Calc (g) = 7.58
Distance Since Last Regen. (km) = 24
Time Since Last Regen. (min) = 55
The Oil Ash Residue = 8.4 and 11%

Time 18:58
The DPF capacity = 100% (regeneration is about to start)
Soot Mass Calc (g) = 23.78
Distance Since Last Regen. (km) = 29
Time Since Last Regen. (min) = 58
The Oil Ash Residue = 8.4 and 11%

Time 19:20
The DPF capacity = 16% (regeneration is complete)
Soot Mass Calc (g) = 3.86
Distance Since Last Regen. (km) = 4
Time Since Last Regen. (min) = 2
The Oil Ash Residue = 8.4 and 11%

Time 21:40
The DPF capacity = 23% (dpf running at normal level)
Soot Mass Calc (g) = 5.38
Distance Since Last Regen. (km) = 22
Time Since Last Regen. (min) = 44
The Oil Ash Residue = 8.4 and 11%

Time 21:43
The DPF capacity = 100% (regeneration is about to start)
Soot Mass Calc (g) = 23.80
Distance Since Last Regen. (km) = 27
Time Since Last Regen. (min) = 47
The Oil Ash Residue = 8.4 and 11%

Time 22:02
The DPF capacity = 100% (regeneration is complete)
Soot Mass Calc (g) = 6.41
Distance Since Last Regen. (km) = 3
Time Since Last Regen. (min) = 3
The Oil Ash Residue = 8.4 and 11%

As you can see from the information, the Soot Mass value is jumping from 7.58g to 23.78 in a space of 2 minutes and 5.38g to 23.80g in space of 3 minutes. This happens every time.

Also, the Oil Ash residue is stable at 8.4 and 11%, so this indicates there is still life in the DPF, right?

Is this the correct regeneration behaviour of the DPF? Or am i missing something?

A Regeneration is happening every day now, sometimes twice in a day depending on how long i drive for. I suspect it may be some other problem and not the DPF that is causing this?? But i could be wrong??

Unfortunately i cannot attach the log file, as it is saying it is 'invalid extension', so i have pasted the log in the next post.

Please can you check the attached screenshots and log, and may be provide some feedback as to why a regeneration is happening so often, considering that the information does not point to a end of life DPF.

Any help from you would be greatly appreciated.

Thank you.
Attachments
Screenshot_20210318-214343_VAG DPF.jpg
Screenshot_20210318-214042_VAG DPF.jpg
Screenshot_20210318-192032_VAG DPF.jpg
Screenshot_20210318-185828_VAG DPF.jpg
Screenshot_20210318-185538_VAG DPF.jpg
Screenshot_20210318-175554_VAG DPF.jpg

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admin
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Re: Is my DPF finished?

Post by admin » Fri Mar 19, 2021 5:28 pm

The DPF system has some issue for sure. The sudden jump of the soot mass calculated means there is some parameter that the ECU consider out of range or implausible so it work in a sort of recovery mode starting regenerations earlier than usual.

This is often caused by the differential pressure sensor, but this is not always true.
I'd go to a service center as soon as possible.

The ECU anticipates the regenerations to prevent any problem, so you shouldn't risk anything, but obviously these multiple regenerations are not so healthy for the engine and its oil.

caller100
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Joined: Mon Mar 08, 2021 10:13 pm

Re: Is my DPF finished?

Post by caller100 » Sat Mar 20, 2021 12:33 pm

Hello Admin.

Thank you for your reply.

I just realised i forgot to attach the log. Here is the log attached in zip format - Vag_DPF_log.zip

I think it may be time to either get the DPF cleaned or buy a new one? I am just worried that if i do get a new DPF or clean it, and same problem appears.

I will be visiting the local garage on Monday for a complete diagnostics check.

In the meantime, please can i get your feedback on the logs.

Thank you once again for your support.

Cheers
Attachments
Vag_DPF_log.zip
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admin
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Re: Is my DPF finished?

Post by admin » Sat Mar 20, 2021 3:33 pm

I confirm what I've already written: suddenly the soot mass calculated jumps to the limit value to force the regeneration and the distance since every regeneration is around 30 km, too little.

The DPF replacement should be the last action you can do, first you may change some sensor.
The diagnosis will give you more details.

caller100
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Joined: Mon Mar 08, 2021 10:13 pm

Re: Is my DPF finished?

Post by caller100 » Sat Mar 20, 2021 7:19 pm

Hello Admin.

Sure i will get the diagnostics done first and hopefully get a clear picture of what the problem might be.

Changing my DPF is a last resort.

Thank you very much for your support.

Cheers

Stefan-Audi-A4
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Re: Is my DPF finished?

Post by Stefan-Audi-A4 » Mon Mar 22, 2021 8:45 am

Hello caller100,

do you already have a solution regarding your DPF issue.
I would be interested, because I have exactly the same behaviour with quite similar values at my 2013 Audi A4 Avant quattro 2.0 TDI with 185.000 km.
Besides:
Oil consumtion: 0.7l/1000km
Fuel consumtion: raised from 8l/100km to 11l/100km
My repair shop already changed the DPF temperatur sensor, DPF differential pressure sensor and 2 injectors but until now there is no improvement.

Stefan-Audi-A4
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Joined: Mon Mar 22, 2021 7:06 am

Re: Is my DPF finished?

Post by Stefan-Audi-A4 » Tue Mar 23, 2021 3:21 am

Update:

With the VAG DPF app I observed that every time after 3-5 Minutes driving the car, the calculated soot mass jumps from 5-10 up to approx. 25 and the DPF starts regenerating. The measured soot mass never drops below 20. After 45 Minutes of regeneration the calculated soot mass is about 6-9 and the measured soot mass as already mentioned approx. 20. This behaviour is everyday the same although I drive at least 2 times 30km long distance every day - this should be a perfect environment for a DPF diesel car.

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admin
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Re: Is my DPF finished?

Post by admin » Tue Mar 23, 2021 8:40 am

My personal opinion, absolutely not from an expert, is that the ECU reads all the parameters and "create" the calculated soot mass value. When some parameter doesn't stay in the predefined range or doesn't change in a predefined way, the ECU changes the calculated value to the field regeneration limit to force the regeneration. A normal DPF behavior doesn't contain those soot mass jumps.
The reason could be the measured soot mass value that doesn't decrease as expected, but this is only a possibility that I'm assuming.

Unfortunately I didn't find any detailed official manual or instruction about the DPF system management, all my information is based on personal experience using the app and reading forums on internet.

Probably a real engine expert can help you better.

caller100
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Joined: Mon Mar 08, 2021 10:13 pm

Re: Is my DPF finished?

Post by caller100 » Tue Mar 23, 2021 11:40 am

Hello Stefan-Audi-A4

No sorry don't have solution for my problem. My car is doing a regeneration like twice per day now.

I had a full diagnostics check on my car and unfortunately there was no problem observed with DPF.

Previously i changed the O2 sensor and DPF pressure sensor. I don't know what else to check. May be temperature sensor? Or EGR valve, but not sure if it is linked to DPF problem?

And i don't have many options left, other than to clean/replace my DPF.

Cheers.

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