DPF Diesel Particle Filter Wear Testing using ODB reader

mikeuk said:

I hope someone can help. I have purchased an obd11 and the app. I tested the obd using torque and it worked. But when I use on the app it says connection issue, engine not supported or obd is poor quality. sometimes comes up no data. do I need to drive the car to get a reading or will just idle do. or do I need to get a different obd tool. I could be doing something wrong but cannot work it out. please help.

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zg3409 said:

Hi,

I am sharing some testing of the Diesel Particle Filter used in the 2013 UK specification vehicle. I am hoping my tests will be of use to others, in particular to those considering buying a diesel DPF car, in order to determine if the DPF is close to needing replacing, but also to determine when it needs to be replaced, and what driving styles are needed for DPF equipped cars.

Back round
I bought a non Golf diesel a few years back and had lack of power and hiccups in power. This was traced to a blocked DPF in addition to a worn/faulty DPF differential pressure sensor hose. In the process of performing DIY diagnosis, I learned you can read the DPF values using the ODB II data port in the car.

Recently I purchased a late 2013 year 1598cc Golf MKVII diesel with DPF and I naturally wanted to check the DPF to see if it OK and to determine when it might need replacing.

DPF Theory and practice
The DPF was added to most diesel cars to collect the black soot that belched from the exhaust of diesel cars, and instead burn it. In some cars passive regeneration (burning) happens during normal use when exhaust temperatures naturally rise to 250 Celsius. In the MKVII I believe the exhaust temperatures are naturally lower.

Meanwhile most cars have a sensor to check how blocked the DPF is. Normally this is a differential pressure sensor where 2 hoses come from before and after the filter, and so the car can use the difference to determine the amount of blockage.

If the car determines the filter is fairly blocked, it may decide, based on many factors, to try a special technique to unblock it. This is called automatic regeneration. The car attempts to raise the exhaust temperature to above 500 Celsius for a period of 10 to 25 minutes during which any un-burnt soot should burn off.

However there is also ash left behind which cannot burn off (the same red ash as left behind in a fireplace) and so eventually the DPF cannot be cleared and needs to be removed and replaced. This can be very relatively expensive particularly in older cars and is normally a shock to the owner. If it is not replaced then lack of power, premature turbo failure, and engine damage due to oil contamination can occur.

In my old vehicle the DPF could be in a bad way, but generally no errors lights would appear and the owner would be none the wiser. Error codes not lighting the lamp would be stored in the ECU and the dealer may notice them if they plug in during routine maintenance. I think the MKVII is more likely to warn the driver, but I would like to know the amount of ash, and hence the life time left in the DPF.

More of DPF here:
http://www.vwaudiforum.co.uk/forum/showthread.php/147028-DPF-information

and:
https://www.dieselnet.com/tech/dpf_ash.php

I know the dealer can plug in and get all sorts of fancy readings. I also know some back street garages have expensive VAG readers costing hundreds of euro. I wanted a lower cost alternative.

Most basic readers will display error code numbers, and some common sensor readings such as temperatures etc. To read MKVII DPF when there is no error code you need some device proven to work and display or calculate relevant values. The basics are differential pressure (how blocked it is), and pre and post DPF temperatures. The main use of the temperature is it can tell when an automatic DPF cleaning cycle has started, and this you can determine how often they are running, and so see if it is working like new or running too often which is an indication of high ash and possible DPF end of life. As I said there may be no lights on the dash, but the cars computer may know something is up, and be storing error codes.

From my other non VW I had a ODBII reader. This is a low cost general reader. In order to get them to work above basic level, you need software or an app, that understands manufacturer specific codes. I found such an app, only recently launched that works with the diesel MKVII and is specific for reading and diagnosing DPF problems.

I want to use this before I have a problem to check the DPF and confirm the APP works, so later down the road I can determine if it needs replacing or possibly sell the vehicle before it needs this major service.

The app I found is called VAG DPF and VAG DPF Free. You need an android phone with bluetooth, and a compatible ODB II bluetooth car interface.

In terms of interfaces, there are lots of low cost devices on line, however 99% are cheap knock off clones, and many work with basic readings, but not with advanced features such as needed for the DPF diagnosis.

There is a generic name ELM327, but genuine units cost 80 Euro, hence all lower cost units are some form of knock off.

The app writer recommends "OBDLink LX,(bluetooth)" and I used "Konnwei ODB link KW902 (bluetooth)" but beware you probably should be paying 30 Euro upwards of a possibly compatible unit. Even then there is no guarantee and you should only purchase a unit you can easily return with low shipping.

In use you first need the hardware. Plug it into the ODB port under the steering wheel. The engine needs to be "on" or at least key turned to red lights. I recommend using a simple free app like "torque" to confirm the hardware can do at least the basics. You may need to turn blue tooth on, and go in to the bluetooth settings and "pair" your phone and enter a pin which is normally 1234 or 0000. Using the torque app you can read basic parameters such as engine temperature and possible error codes. When driving you can see vehicle speed etc.

Once torque is working then you move on to VAG DPF Free. This helps check if the hardware is really fully compatible, and displays enough to see if regeneration is occurring. Assuming all is well you may consider paying a small amount for the extra features on the non free VAG DPF. This is what I have done and I hope to check the DPF over the coming weeks and years.

So results?, well I have none so far. I have confirmed that it is working and compatible, but I think I need to do a few long journeys before the app can calculate all the values. What I do know is my MKVII has a Engine code CHLA, and a type E4 1.6L EDL. I know it had travelled at least 187km without needing a regeneration, but I also know the DPF in general may need replacing at 100,000 miles and should be checked at every 10,000 miles after that. DPF life can be far less particularly with city & low mileage cars.

I would like others to compile their results and compare to mine over the years/miles. If you are in the UK/IRL I could loan/send you my hardware. I would be particularly interested in those with the original DPF with 100,000 + miles on the clock.

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zg3409 said:

I managed to monitor a regeneration in progress. Attached is an image taken of the screen. The interesting points to note are:

Regeneration started at 70% full DPF. After regeneration it dropped to 20% full and stopped. Does this indicate the 20% ash (not soot) could not be cleared?) Regeneration took around 15 minutes driving at 100km/h (60mph). Regeneration happened at around 370km (230 miles) 307 minutes (5 hours driving) since last run. This probably indicates the DPF is fairly OK. Very frequency regenerations indicates a problem with either the engine producing abnormal soot, or the DPF nearly full with ash. The mileage on the car is 60,000km (37,000 miles) The car is 3 years old so average of 20,000km(12,000miles)/year.
I would be interesting in seeing others values in particular new and old cars.

You can see the exhaust temperature rose to 598 Celsius, and the graphic changed from green to red.

Another thing interesting happened while dual carriageway driving. While driving really aggressively the exhaust temperature rose to above 350 Celsius and "accidental" regeneration started. This means the graphic changed to red, the amount of soot (mg) became minus instead of positive. Very quickly it stopped, and then it started and stopped a couple of times. So some people say the MKVII cannot do regeneration during normal driving, but I have proven it can at least for a minute or two.

Again I can loan the hardware to others to compare readings, as I am interested in readings at different mileages

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Rick86 said:

Hi,

I'm using the same scan tool and app.

I have covered 36652 miles and have 17.3 (oil ash g). - 22% full

How many miles has your car covered?

Thanks,

Rick

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zg3409 said:

I managed to monitor a regeneration in progress. Attached is an image taken of the screen. The interesting points to note are:

Regeneration started at 70% full DPF. After regeneration it dropped to 20% full and stopped. Does this indicate the 20% ash (not soot) could not be cleared?) Regeneration took around 15 minutes driving at 100km/h (60mph). Regeneration happened at around 370km (230 miles) 307 minutes (5 hours driving) since last run. This probably indicates the DPF is fairly OK. Very frequency regenerations indicates a problem with either the engine producing abnormal soot, or the DPF nearly full with ash. The mileage on the car is 60,000km (37,000 miles) The car is 3 years old so average of 20,000km(12,000miles)/year.
I would be interesting in seeing others values in particular new and old cars.

You can see the exhaust temperature rose to 598 Celsius, and the graphic changed from green to red.

Another thing interesting happened while dual carriageway driving. While driving really aggressively the exhaust temperature rose to above 350 Celsius and "accidental" regeneration started. This means the graphic changed to red, the amount of soot (mg) became minus instead of positive. Very quickly it stopped, and then it started and stopped a couple of times. So some people say the MKVII cannot do regeneration during normal driving, but I have proven it can at least for a minute or two.

Again I can loan the hardware to others to compare readings, as I am interested in readings at different mileages

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razvanrudy said:

Just give it a try and my first screenshot is

I will see how is going

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bakili said:

Can someone explain SOT mass and Oil Ash? Which one indicates that dpf is full?

Sent from my SM-G930F using Tapatalk

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zg3409 said:

20%/23% after regeneration seems normal

razvanrudy at ?miles, around 2 gram of ash, regen every 429km
amcneill at 7,500 miles, around 3.5 gram of ash, regen every 390km
me at 37,000 miles, around 12 gram of ash, regen every 370km
bakii at 74,000 miles, around 25 gram of ash regen every 420km

bakii I am guessing your DPF is half full of ash. So if it is at 50% now, I am guessing it may start giving errors at 70 to 100%, which is up to another 75,000 miles. 45 grams of oil ash seems to be replacement value:

From here:
http://forums.tdiclub.com/showpost.php?p=3619546&postcount=94
Per VW and VAGCOM, the DPF needs replaced when the volume = 45 grams (380 ml), although in the thread they say they are not sure. It could be that the car will refuse to regenerate, if there is soot and ash of 45g, as it thinks the DPF is so blocked it can never unblock it, not that it is full of only ash.

razvanrudy what is your mileage?

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zg3409 said:

The DPF contains soot (black stuff) and ash (red stuff) the same as a fireplace. Regeneration can burn off soot but cannot remove ash.

If your DPF is nearly full of ash it will need to regenerate very often, This value is calculated I assume after each regeneration is completed and should never go down unless the DPF is replaced.

To answer your question, soot mass is what starts a regeneration, but there are other factors that come in to play such as engine temperature and distance since last regeneration. The green bar shows you how close to starting a regeneration it is.

Most of these values are calculated by measuring the pressure difference across the DPF then calculating/guessing the reasons for the pressure difference.

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