Slow Regen Seat Leon CRLB

[Happax]

Hi All, hopefully someone can shed some light on the below:

I recently bought a Low mileage (27000 miles) 2016 Seat Leon 2.0 TDI. The previous owner had recently had the DPF cleaned to the tune of £1100! Since owning it I have had the DPF light on multiple times. This amazing app has revealed it isn't that the soot levels are particularly high as they do very slowly start to drop but in fact the car is unable to effectively regen in any sort of normal driving so after an extended period of time it pings the light on. The maximum drop rate of soot I seem to be able to achieve is about -300mg/mi and not consistently I've seen some people get well into the thousands during a regen so was wondering what might be going on.

The Oil level was high when I first bought it which I thought was the cause but I have since serviced and dropped the level and although the regen smell is better it still tries to regen every few days. The engine also doesn't appear to be burning oil or losing coolant.

The only way I can get the car to fully clean it self is with an exceptionally long drive up the motorway in 4th or 5th gear otherwise it just can't clear itself at all.

I should add the 'measured soot mass' which isn't measured on this app is always in the negative??

The Exhaust gas temperatures seem to be slightly lower than most I've seen too. Hopefully you can see in the attached screenshot.

[admin]

The regen process seems a little weak if the input gas temperature is always near 533 degrees like in your screenshot and the charge rate is 300mg/mi. The temperature usually stays over 600° and the charge rate can easily exceed 1000 mg/mi.

Have you verified if this temperature is higher when you drive in the highway? A low temperature can be justified if you frequently release the accelerator pedal driving in the city.

What the app shows when you see the warning light on? Is the soot mass value higher than 100%?

The measured soot mass is a strange value, is reports useless values when the engine is running fine, but it shows a realistic soot mass value when there is issues in some part of the PDF system like a faulty sensor.

[Happax]

Thanks for the reply,

No the DPF light comes on when it is well below 100%, It can regen, it is just exceptionally slow and I think it times out after a couple of hours or so and pings the light on.

When on the motorway it is much as can be seen in the screen shot, it takes quite a decent amount of time to get the soot rate to start dropping so it has to be up to speed/revs for a while before it starts burning off.

I have ordered new pressure sensors and a new Pre-DPF temp sensor but I am doubtful it is the cause.

My concern is that the previous owner didn't address the dpf issues for a long time and the car has been driven with post injection on consistently and consequently the engine has suffered because of it, maybe the injectors need cleaning/calibrating or maybe there is a small amount of oil being burnt.

I may also try and get Seat to wipe/flash the ECU with the latest software to see if driving behaviour models are the root cause.

Let me know what you think

[admin]

First you could check if the ECU resisters some error that can give you more information.
It's not normal to see the dpf warning light if the soot is below the field limit.

Of course the problem can be everywhere in the engine, the best way to solve quickly is to find someone who deeply knows the dpf and its problems.
The sensors replacement can be the first step to solve the problem avoiding high expenses.

Did you find any similar problem in other forums?

[Happax]

No I haven't seen any issues the same anywhere else.

The Soot mass measured I can see functioning normally as during a regen its value will drop a good 20 grams or so. This makes me think the DPF is working correctly but the soot mass calculated figure won't drop quickly as the output temps don't get high enough to satisfy the algorithm. Consequently the car flags a fault code for dpf regen duration.

[admin]

Yes I agree, the ECU probably has ranges in which the process must stay. If it goes out of range, a warning lamp is lit.

[Happax]

Just a small update on this, I have just noticed that my version of the EA288 engine (CRLB) doesn't actually have a post-DPF exhaust temperature sensor.

Does anyone know how the ECU calculates DPF output gas temperature without this information? The app seems to be reading this parameter fine!

[admin]

In the SSP608 there is the CRLB engine and I see also the exhaust gas temperature sensor 4 that is placed right after the DPF.
It should be called sensor G648 and the value can be read, as you said.
Why do you think is isn't present?

[Happax]

I have visually checked and can see that there is only a pressure tube for the differential pressure sensor and a lambda sensor post-DPF. I have also checked the wiring diagrams for post May 2016 CRLB Seat Leon's and they only show EGT sensors 1,2 and 3 present.

Are you able to link a copy of the SSP on here?

[admin]

Can be checked here:
https://procarmanuals.com/vag-ssp-608-a ... i-engines/

On page 44 you can see the "Exhaust gas temperature sender 4 G648"

[Happax]

No sorry, as of May 2016 they removed the G648 sensor post DPF, at least within the Seat Leon's. I can't speak for other applications.

I have managed to solve my problem though. The car had had the DPF removed to be cleaned and it looks like the technician managed to screw EGT 2 and EGT 3 in back to front upon reassembly. Temperatures on the input side are now sufficient for the calculated output temps to be high enough to satisfy the calculated soot algorithm.

Many thanks for your help and just for your great app in helping diagnose this issue!