Hi, just purchased a 2015 Octavia RS 2.0 TDI with 238k km / 147k miles. At the end of the 3 hour drive back home after picking it up, i got a DPF warning light, which seems strange after driving for 3 hours straight. But the car was running fine with normal performance.

 

Anyway when i got home i plugged in my Autocom diagnostics tool (i have ordered a VCDS) and ran diagnostic for checking soot amount. It was reading 68 grams and it says 80 grams is the limit before needing to replace the DPF. So i forced a regen and during regen its reading 17 grams for some reason, im not sure which reading is the correct one. However after 30 mins during regen it failed and stopped the process, and soot amount was only down to 16 grams. And i noticed the DPF only reached a peak temperature of ~560 degrees celsius, which seems kind of low and probably why it failed and stopped the process. So i tried it again and this time it also failed during regen but with a peak temperature of ~588 degrees, which still seems kind of low. Outside temperature was somewhat chilly at 9 degrees celcius but that shouldn’t matter.

 

This was 2 days ago and ive driven the car since, and its driving like normal and dpf light havent come up again, but i have noticed that every time i shut the car off, its keeping the cooling fans running for a couple minutes. Its happening exactly everytime i shut the car off, and without being driven hard at all. I assume this is dpf/regen related. 
 

Anyone have any suggestions to what is going on?

That's nothing to worry about. I've driven trips of hundreds of miles and the same, I've driven short trips and the car has kept it's fan running after I've stopped.

 

It's just cooling itself off, usually whilst the car has been turned off when am active regen is taking place (can usually tell that because of the funny smell when you get out the car)

At around 230,000km the car should have the oil ash mass read out, then every 30,000km after.

This is the material that cannot be burnt off, and as the exhaust gets closer to the limit, the regen frequency increases as it's more blocked.

 

The other 2x values that you should read is Soot calculated and Soot measured, when either one of these reaches 22g, then active regens will take place.

As the name implies, one is measured by the DPF differential pressure sensor(s) and is a physical reading, the other is calculated by time/distance and won't read the same as your measured (think of it as a failsafe)

 

When you get your VCDS, you should measure the values of the 3 MVB's (Measurement Value Blocks)

If the soot values are near 22g, then perhaps you should do one more static regeneration to get a baseline of what's going on.

 

I found that my Soot measured didn't go under 15g during regeneration, so had to abort it.

I then took it to a friend of mine, and at his garage we put in some cleaner, and then after this the Soot measured dropped to under 1g.

 

 

When you do the regen with VCDS, you can open up MVB's during the process, so you can bring up Soot measured, Soot calculated, then you can bring up measuring blocks for exhaust temperatures.

Sorry for the poor screenshot, taken on phone not PC

@varooom Can anything be done with the oil ash mass ?. Mine's at 40.6g for a 2015 octavia 1.6 with just over 180k km on the clock.

 

Not sure if that's good or bad going but it's half way to the 80g limit.

soot mass measured = 2.94g & soot mass calculated was 13.32g at time I took the readings.

1 hour ago, lway said:

@varooom Can anything be done with the oil ash mass ?. Mine's at 40.6g for a 2015 octavia 1.6 with just over 180k km on the clock.

 

Not sure if that's good or bad going but it's half way to the 80g limit.

soot mass measured = 2.94g & soot mass calculated was 13.32g at time I took the readings.

That oil ash comes from material in the oil that cannot be burnt into smaller particles.

 

The value for your car is nothing to worry about, wait until you get to 230k km and measure again then, and every 30k km after.  The higher the value, the more frequently the car will try to regenerate to maintain health.

 

In particular, your soot measured is lower than the car thinks, so is a very good thing, sign of a healthy DPF.

I noticed that everytime before i shut the car off and the fans stay on, idle rpm is about ~900. Yesterday for the first time when i shut the car off after driving at 110 km/h for 30 min straight, the fans shut off immediately aswell. That time, idle rpm right before shutting off was 600-700 rpm. Does this for sure mean that the car is in the middle of an active regen when im shutting the car off? If so its very strange, cause its happening almost everytime. I received my VCDS today, so will be plugging it in to check soot values.

Your car was able to complete the active regeneration before getting home, which is why your fans weren't running and revs were in the normal range.

 

The car is in the majority of the time trying to do active regens, I guess you maybe use the car for shorter journeys?

20 hours ago, lway said:

@varooom Can anything be done with the oil ash mass ?. Mine's at 40.6g for a 2015 octavia 1.6 with just over 180k km on the clock.

 

Not sure if that's good or bad going but it's half way to the 80g limit.

soot mass measured = 2.94g & soot mass calculated was 13.32g at time I took the readings.

 

You can tell the ECU that the unit has been replaced and it will then start counting up from zero again, if like me your measured vs calculated readings are drastically different then there is no harm in doing the reset, I have.

 

I know now that when the ECU finally says "No more!" it will be from having measured the back pressure (differentiel) and knows the DPF is blocked rather than based on a very flawed calculation.

 

I also paid to have the Emissions Fix rolled back, the rate at which the calculated soot mass rises is much slower although still far more than the measured, it's very very rare indeed that I am aware of a regen these days, before it was all the time.

2 hours ago, varooom said:

Your car was able to complete the active regeneration before getting home, which is why your fans weren't running and revs were in the normal range.

 

The car is in the majority of the time trying to do active regens, I guess you maybe use the car for shorter journeys?

I drive plenty, both to/from work but also on my spare time. Before this car, i had a Kia Ceed -2010 for 6 years, also a diesel. During these years i put 170,000 km on the odometer and its now at 370,000 km, and never had an issue with the DPF. It barely even did any active regens either. But i suspect the previous owner drove this Octavia for short trips.

3 minutes ago, Orman said:

I drive plenty, both to/from work but also on my spare time. Before this car, i had a Kia Ceed -2010 for 6 years, also a diesel. During these years i put 170,000 km on the odometer and its now at 370,000 km, and never had an issue with the DPF. It barely even did any active regens either. But i suspect the previous owner drove this Octavia for short trips.

It will be interesting to see what you can find out with your new VCDS cable, might be an idea to so a full car scan and post up the log (can see the firmware loaded for engine ECU) you might find the car has had the NOx emissions fix, I am sure they regen more afterwards.

 

 

19 minutes ago, J.R. said:

 

You can tell the ECU that the unit has been replaced and it will then start counting up from zero again, if like me your measured vs calculated readings are drastically different then there is no harm in doing the reset, I have.

 

I know now that when the ECU finally says "No more!" it will be from having measured the back pressure (differentiel) and knows the DPF is blocked rather than based on a very flawed calculation.

 

I also paid to have the Emissions Fix rolled back, the rate at which the calculated soot mass rises is much slower although still far more than the measured, it's very very rare indeed that I am aware of a regen these days, before it was all the time.

The oil ash reset should only tell the car it has a new exhaust, it's always been an estimate of how much based upon what VAG have done in their testing.

 

I don't see how resetting oil ash mass would have an impact on the Soot calculated though?

Rolling back to a pre-NOx ECU version for sure, they cheated a lot despite their claims to the contrary.

It didn't, I was simply answering the question.

 

I don't know for sure that when an ECU has calculated that a DPF  has 80g of oil ash but the differential pressure is fine and dandy that it will actually say game over and go into limp mode but I did not want to find out.

 

Call it anxiety if you like but I dont want to undertake a long journey at a higher mileage and be concerned about "Computer says NO!"

As long as every time I check using VCDS I find that the measured soot is far less than the calculated then I am a happy anxiety free bunny!

 

Having had the "fix" rolled back I am no longer concerned about the fuel wasted and the possibility of oil dilution from what were far too frequent regens, even now only one in three that happens should happen but they seem to complete in the same driving cycles where before they would not and try again each and every subsequent journey until I did a similar distance but on faster roads.

5 hours ago, varooom said:

It will be interesting to see what you can find out with your new VCDS cable, might be an idea to so a full car scan and post up the log (can see the firmware loaded for engine ECU) you might find the car has had the NOx emissions fix, I am sure they regen more afterwards.

 

 

The oil ash reset should only tell the car it has a new exhaust, it's always been an estimate of how much based upon what VAG have done in their testing.

 

I don't see how resetting oil ash mass would have an impact on the Soot calculated though?

Rolling back to a pre-NOx ECU version for sure, they cheated a lot despite their claims to the contrary.

Hi, plugged in VCDS to do a regen and this is the values showing. Seems kind of low, why is it trying to do an active regen all the time then?

25 minutes ago, Orman said:

Hi, plugged in VCDS to do a regen and this is the values showing. Seems kind of low, why is it trying to do an active regen all the time then?

See if you can find anything on time/distance since last regen.

 

Mine even put the exhaust lamp on the other week, but soot values similar to yours.

 

They have many fail-safe features, soot calculated, and also time/distance since last regen.

Tha fact that your measured value is significantly higher than the calculated (or even higher at all) is a cause for concern, the diff press sensor is indicating that the DPF is obstructed, it may be a sensor failure or one having been replaced and not calibrated but I would not expect the measured value to exceed tha wildly pessimistic calculated one.

 

I would check how many kms since the last regen, beware it expresses the value in metres! Typical of the rubbish put out by VCDS, I dont know if its them or VAG to blame but you simply cannot trust many of the units or their +ve & -ve values.

 

I would keep an eye on the readings and see how quickly it rises and also test the diff press sensor reading at idle and the max 2.5k RPM you can do at a standstill, if you have a passenger who wont get carsick looking at the laptop screen then check it while driving.

To answer your question, and this is only speculation on my part, its trying to do a regen all the time because it hasn't been able to complete the previous ones, 8.71 grammes is probably above the regen completed threshold, you will find what it is amongst the millions of VCDS measuring blocks, 3 grammes rings a bell for my engine.

 

I have moved to a new area and my journey profiles have changed, before having the emissions fix rolled back 20km journeys locally on windy slow back roads were sufficient to get a regen started but never to complete, the fans were running pretty much every time I stopped day after day and I would have to go for a thrash just to allow one to complete, that was bad enough but the frequency was so often I would be driving the car as much to please it as to please myself, the final straw was doing an 800km autoroute journey towing a massively overloaded trailer with a huge frontal area, i was on full throttle on every slight incline and the oil temp was sitting at 116°c, if that did not achieve a passive regen then nothing would but the day after I arrived it was trying once again to regen, calculated value 23g, measured value 0.5g

 

It had actually regenned during the drive down several times as well!

 

That was the final straw, I had the ECU software rolled back and I hear the fans running after switch off maybe once every 3 months and then only after lots of short journeys, its still regenning more than the measured values would require but nowhere near like before.

Edited 11 November, 20223 yr by J.R.

On 11/11/2022 at 19:21, varooom said:

See if you can find anything on time/distance since last regen.

 

Mine even put the exhaust lamp on the other week, but soot values similar to yours.

 

They have many fail-safe features, soot calculated, and also time/distance since last regen.

Here is some values I pulled from VCDS. This is after 6 hours of almost straight highway driving after a journey I did today. 

 

Edited 12 November, 20223 yr by Orman
Edited picture

Soot is coming down nicely, I guess you will probably need to budget for a new exhaust, or cheat and tell the car it has a new one fitted.

1 minute ago, varooom said:

Soot is coming down nicely, I guess you will probably need to budget for a new exhaust, or cheat and tell the car it has a new one fitted.

But how come the car starts to actively regen with only 5,58g of measured soot, exactly every time I go out and drive? On longer drives, even on straight highways, it will even pop up with a check DPF warning.

If you are driving down a motorway, but not above 2,000 rpm (or what the car needs) then after 60 minutes it will put on the exhaust lamp due to "failed" regens.

Just today I drove down at least 15 miles of motorway above 2,000 rpm, when I got home it was still trying to regen, they are strange how they act.

 

Your exhaust is getting very near end of life, so it is going to be doing regular regenerations to try to keep the soot from blocking and then you cannot do any regens at all.

I think this is normal as the exhaust gets near end of life, as in early years the generations are less (this is how it seems to me)

5 minutes ago, varooom said:

If you are driving down a motorway, but not above 2,000 rpm (or what the car needs) then after 60 minutes it will put on the exhaust lamp due to "failed" regens.

Just today I drove down at least 15 miles of motorway above 2,000 rpm, when I got home it was still trying to regen, they are strange how they act.

 

Your exhaust is getting very near end of life, so it is going to be doing regular regenerations to try to keep the soot from blocking and then you cannot do any regens at all.

I think this is normal as the exhaust gets near end of life, as in early years the generations are less (this is how it seems to me)

Hm, on the way back home I drove for 2,5 hours in sport mode at highway speeds (mostly 100 km/h+), which kept it between 4th and 5th gear and 2500-3000 rpm. Still the dpf light came on.

 

The instruction manual says to drive between 1800-2500 rpm at speeds above 70 km/h for dpf to regen correctly, so I was well above that.

My own 1.6TDI with same mileage as yours (very close) behaves same.

Soot good

No indicated faults in engine

 

Yet it tries to do regens frequently, so it must be ECU making these requests often to make exhaust not clog up with too much soot.

The only common factor is exhaust is nearing end of life, so the car will be performing more frequent time/distance fail safe regens (where it totally ignores soot values!)

 

This is my own understanding, you could to test reset the exhaust to 0mg of oil ash, and then see if the regens stop being as frequent... this will then let the car revert to soot based regens as priority, and increase the time/distance regens.

 

Hell, I will probably do this with my own, as it tries to regen 9/10 journeys, and has put exhaust lamp on... and the soot is low.

1 minute ago, varooom said:

My own 1.6TDI with same mileage as yours (very close) behaves same.

Soot good

No indicated faults in engine

 

Yet it tries to do regens frequently, so it must be ECU making these requests often to make exhaust not clog up with too much soot.

The only common factor is exhaust is nearing end of life, so the car will be performing more frequent time/distance fail safe regens (where it totally ignores soot values!)

 

This is my own understanding, you could to test reset the exhaust to 0mg of oil ash, and then see if the regens stop being as frequent... this will then let the car revert to soot based regens as priority, and increase the time/distance regens.

 

Hell, I will probably do this with my own, as it tries to regen 9/10 journeys, and has put exhaust lamp on... and the soot is low.

Hm, it does actually show 69 g oil ash as the picture I posted above, and max limit is 80. How do i reset to 0g of oil ash? Can it be done with VCDS? If so, please tell me how.

4 minutes ago, Orman said:

Hm, it does actually show 69 g oil ash as the picture I posted above, and max limit is 80. How do i reset to 0g of oil ash? Can it be done with VCDS? If so, please tell me how.

http://wiki.ross-tech.com/wiki/index.php/2.0L_CR_TDI#Adaptation_of_Carbon_Mass_.28after_DPF_Replacement.29

 

You can try this, but don't shoot messenger, this is telling your car you have fitted a new exhaust!

I don't mind doing this on my car at all, as I am sure I will just run it into the ground so to speak.

14 minutes ago, varooom said:

http://wiki.ross-tech.com/wiki/index.php/2.0L_CR_TDI#Adaptation_of_Carbon_Mass_.28after_DPF_Replacement.29

 

You can try this, but don't shoot messenger, this is telling your car you have fitted a new exhaust!

I don't mind doing this on my car at all, as I am sure I will just run it into the ground so to speak.

Hm, this will basically reset all values to zero thinking the DPF is brand new right This sounds like a workaround, but surely will cause issues in the future?