TDI: Frequent Regeneration? Where Does All the Soot Come From? (Solution)

Hello, hello.
I'm mostly just a reader here, and I've already searched the entire forum, but I haven't found a solution to my problem.
Problem vehicle: Sharan 7N 2.0 TDI, common rail diesel with SCR catalytic converter, 103 kW, engine code: CFFB.
Diesel engine EA189 affected by the "Dieselgate" scandal, with software update applied approximately 70,000 km ago. Current mileage: 197,000 km.
My problem:
"For the past three weeks, the fan has been running regularly for over three minutes after the engine is turned off, even after short trips. The water temperature sensors are providing logical values, and the fan should not run after the engine is turned off, as the water temperature is not in the critical range. The start-stop function is not available once the water temperature reaches 90 degrees Celsius as indicated on the instrument cluster."
Two weeks ago, during a full system scan, the following error was detected:
15733 - SCR NOx catalyst, bank 1.
P20EE 00 (096) - Efficiency too low.
Sporadically - Unconfirmed - Verified since last deletion.
The inspection of the cables and connectors revealed no abnormalities. The error was cleared, and it has not reappeared since.
The fan is still running continuously, and the start-stop function is still not available when the engine is warm.
I have to mention that my wife drives the car, and I don't always have access to it. However, I took very good care of the patient over the weekend.
When the ventilation system is running, very hot air flows underneath the car, which for me is a sign of a potentially failed regeneration process. I haven't been able to determine how many times the regeneration process has failed using VCDS; in the relevant section, I found a value of 0.
I proactively replaced the differential pressure sensor last week; it can't hurt, and the line to the DPF is clean.
It's now quite remarkable that the car seems to be regenerating its battery every day, considering a daily commute of 80 kilometers (approximately 50 miles) each way on federal and state roads. So far, my wife hasn't noticed the regenerations, and neither have I, honestly; everything has been completely inconspicuous.
Yesterday evening, after a 60-kilometer drive on the federal highway at approximately 120 km/h, the DPF (Diesel Particulate Filter) light came on. Upon arrival, I let the car idle until the engine speed dropped from just below 1000 rpm to its normal speed. The fan continued to run for a short time, but the DPF light was off.
On the way back, the DPF light came on again after about 40 kilometers, but I stopped the car because it was already late.
Today, I drove the car for about 50 kilometers and logged the values that seemed logical to me, which I've attached in a file. It regenerated well again, and the DPF light didn't come on. I'm just puzzled by the rapid increase in soot mass at the beginning, so I also logged the exhaust gas recirculation (EGR) data.
Surprisingly, I haven't experienced any oiliness!
I'd like to share this file now, but I won't comment on it further. Maybe someone here has a solution; I'm feeling a bit stuck at the moment.

Sure, here's the translation:

"Thank you in advance!"
Regards,
Ralf.

Hi,

Thank you! Unfortunately, the log shows the air mass in g/s instead of mg/cycle, which makes it difficult to compare with empirical values.

You can check yourself if the target air mass value in the partial load range is approximately equal to the actual value, and whether the actual value doesn't reach astronomically high values when the engine is running at full throttle (which would indicate a vacuum or air leak).

Anything that causes excessive soot production is a potential issue, particularly insufficient combustion air in the cylinders or defects such as oil leaks caused by a faulty turbocharger bearing.

The most likely causes would initially be damage from martens gnawing on the charge air hoses, or cracks in the charge air hoses or the intercooler. These are often indicated by oil stains.

Best regards, Rainer.

Thank you very much, Rainer!

I took another test drive today because I wanted to see exactly if there was any leakage. I've attached the log file. The air mass is specified in mg/stroke!
I'm going to take another look at it myself, but as they say, two heads are better than one.
Are the values from the differential pressure sensor plausible? Everything I've found in this forum suggests that the readings should be lower when the system is idle. Since I need to access the extended measurement data, I can't find any target values for the differential pressure anywhere.
Am I correct in assuming that the amount of soot is increasing too quickly, even during the regeneration phase?
I'm sorry that I can't answer what seem like simple questions myself, but the whole topic of exhaust gas treatment didn't exist during my training! I have to do some research every time I encounter a problem like this!

Regards,
Ralf.

I think I've already found something!
At 3200 RPM, the target air mass is 1029.70 mg/stroke, while the actual value is 422.10 mg/stroke!

The turbocharger is fighting against it; it should be at 1.089 bar, but it's reading 2.201 bar. It's strange that I'm not getting any error messages.

I've attached a picture of the disaster!

That means I'll be getting under the car tomorrow to check the hoses and other things.

If I am wrong, I will still slow down!

Regards,
Ralf.

Hi,
Can you please read the message and post it here?
- Particulate filter: Time since last regeneration.
- Diesel particulate filter: Oil ash volume.
- Diesel particulate filter: Calculated soot mass.
- Particulate filter: Measured soot mass.
- Particle filter: Kilometers since last regeneration.
- Diesel Particulate Filter: Fuel consumption since last regeneration.
- Load limit for field regeneration.
- Load limit for service recovery.
- Loading limit
- Overload
- Vehicle distance traveled.
- Diesel particulate filter: Oil ash mass.
This provides an overview of the condition of the particulate filter. You can save these measurement values as a selection (u01 file) and access them at any time.
hg
Herbert.

Certainly!
I just did that!
The engine is off.
I have attached the protocol!

Regards,
Ralf.

Hi,
Immediately after regeneration, the "measured" soot level is already back at or still at its maximum value.
What is the differential pressure sensor reading when the engine is not running?
I am aware of cases where the calculated soot mass is significantly higher than the measured value. This can lead to more frequent regeneration cycles, and these cycles will end when the smaller value approaches zero, without the higher (calculated) value correspondingly decreasing.
If possible, could you please record a regeneration process using the data mentioned above? There's also a status bit that indicates the regeneration status.
hg
Herbert.

The differential pressure sensor showed a reading of 17 after a prolonged period of inactivity. After the last trip, with the engine turned off but still warm, it read 45.

"After work today, I'm going to check the hoses from the turbocharger to the intake manifold. It seems like the air mass is dropping significantly above certain engine speeds, and I suspect there's a leak in the charge air system. This is likely causing increased soot production, which the DPF regeneration system can't keep up with."
I will know more tonight.

I will report!

Regards,
Ralf.

Just came out of the garage, here's my report:

The intercooler system is airtight; I pressure-tested the entire area with approximately 1.5 bar, and there was no pressure loss or hissing.

I'm no smarter than I was before.

Even though I'm probably being annoying right now, I would be very grateful for any further tips.

Could it be that the differential pressure sensor, which is new and original from Bosch, is providing incorrect readings, and is therefore repeatedly triggering the field regeneration? The values it's providing seem too high to me, or do you find them plausible?

Regards,
Ralf.

Zu hoch ist noch vorsichtig ausgedrückt. Bei stehendem Motor sollte der Wert nahe 0 hPa sein. See https://community.dieselschrauber.org/en/viewtopic.php?t=27732.
Where was it purchased? (Not what).
hg
Herbert.

So, the differential pressure at the DPF when the engine is off should be approximately 0 mbar.

The sensor was purchased from a reputable vendor, and I will be getting a new one soon.
Practice makes perfect!

Regards,
Ralf.

Have the sensor selected based on the VIN/parts catalog, not based on the sample.
What is the history of the car (ownership, mileage at the time of purchase, any noteworthy issues)?
hg
Herbert.

The friendly person did the same thing the first time!

I bought the car when it was three years old and had 126,000 km (approximately 78,000 miles) on the odometer. It was a company car for an employee. Now it has 197,000 km (approximately 122,000 miles). It averages about 30,000 km (approximately 18,600 miles) per year, and most of the driving is on country roads and highways, with very few trips shorter than 40 km (approximately 25 miles).

Maintenance up to 126,000 km at a certified service center, after that by me!

No unusual occurrences in the last 70,000 km.

Regards,
Ralf.

Hi,
It's just speculation, but if a particulate filter is full (with ash), then...
- if the differential pressure becomes too high,
- regenerates the DPF very frequently.
- The exhaust flow is reduced due to back pressure, which in turn reduces the boost pressure and air mass (this becomes noticeable at high target values).
The ash loading value is a variable calculation.
hg
Herbert.

I will continue my research this weekend.
Okay, gib mir den deutschen Text, den du übersetzt haben möchtest. Ich werde dir dann nur die englische Übersetzung geben.

Best regards,
Ralf