Fehlercode P0299 - Ladedruckregelung-Regelgrenze unterschr. | Posts 16+

Hello,

Quote:

5360 rpm, Target: 1820.0 mbar, Actual: 1610.0 mbar.

I still suspect that you have a leak in the boost pressure system, through which air is escaping.
Furthermore, the car has fewer horsepower than what is considered "functional."

Best regards, Rainer.

Hello Rainer,

It's possible that... A badger has made a nest in our underground garage.

That means I need to check the turbocharger boost pressure. I'll have to see if I can do it myself before my workshop space is occupied by the caravan; otherwise, I might have to get someone else to do it.

If I manage to get it working again, could I release the pressure on the intake side before the turbocharger and seal off the hose at the throttle body, or would that damage the turbocharger?

Greetings,
Dennis.

Here's another tip: You can also check the learning values for the lambda control system from the engine control unit. Larger negative values also indicate leaks in the charge air system (or, for example, leaking fuel injectors, meaning that the fuel/air ratio is too high).

Best regards, Rainer.

Hi,

Thank you for the tip. I followed your instructions and checked the learning values. I hope I'm looking at the correct measurement block (MWB 32). I suspect that the left value represents idle, and the right value represents full load. At least, the values were updated during driving in those conditions.

My driving profile for the last 200 km looked like this: I didn't use full throttle at all, but instead drove mostly on upgraded federal roads with a speed limit of 80 km/h. The attached Screenshot shows the learned values.

"I also logged the current lambda value under full load. I've noticed that the reading goes bold when at maximum boost pressure, and that the engine seems to run leaner at higher RPMs. Can we draw any conclusions from this? Perhaps it indicates that too little fuel is being injected, which in turn could be causing the boost pressure to be lower than expected?"

The difference between the actual boost pressure and the specified boost pressure roughly corresponds to the engine speed range where the lambda values become positive and greater than 1.

Best regards,
Dennis.

Hello,

Unfortunately, the percentage deviations in your lambda values look good.
The boost pressure control system, as the name suggests, is a closed-loop system. Deviations as large as yours indicate that something is not working correctly.

The engine control unit injects enough fuel so that the desired lambda value is achieved for the available air.

The small percentage adjustment values in your lambda control now allow us to draw the following conclusions:
- Approximately the amount of air that enters the engine is what the mass airflow sensor actually measures.
- Consequently, no air is lost, for example, due to a leak.
- The amount of air entering your engine is still too low due to insufficient boost pressure.

If you perform a full-throttle test and compare the air mass readings with another vehicle, you will likely find lower air mass values in your own vehicle.

Possible reasons for low boost pressure could include a wastegate that is not closing properly on the turbocharger, or blockages in the exhaust system.

Best regards, Rainer.

At least, we can now narrow down the error a bit .

The stuck wastegate makes sense in this context. The turbocharger can build up full pressure until the N75 valve intervenes. However, if the N75 valve closes and the wastegate remains open, it's clear that full pressure cannot be achieved.
Conversely, this would suggest that if I accelerate with a light load at 4000 rpm, there shouldn't be any problems.

If I'm not mistaken, this would also explain the stored boost pressure of 970 mbar in the freeze frame data. Gear change --> turbine slows down --> full throttle with the wastegate valve open --> no build-up of boost pressure.

Could the machine be repaired and made functional again, or is a new loader required?

By the way, thank you very much for the great support and for being available on Sunday evenings.

Greetings.
Dennis.

Quote:

Could the construction be made functional again, or is a new loader required here?

Good question. You should open it up and take a look. At the very least, you should be able to see the wastegate valve if you simply remove the turbocharger.
It could also be related to the wastegate valve or its control system; I've experienced issues with those sticking before.

Best regards, Rainer.
PS: In theory, for example, the mass airflow sensor could be measuring too low, an injector could be clogged, and there could also be a leak in the charge air system (or similar combinations). However, this is less likely due to the sheer number of potential faults.

I probably won't have any other choice. The N75 is new, so it's likely not the problem. I'll see if I can convince someone to do it with me. I don't feel comfortable doing it alone.

Otherwise, he'll just take it to the workshop.

I logged the air mass earlier. The maximum value was 154.69 g/s. Before the chip tuning, it was 137 g/s.
Furthermore, I floored the accelerator in 3rd gear at various RPMs to test whether the turbocharger is functioning properly in the RPM ranges that showed insufficient boost pressure in the previous logs.

"I particularly notice in the log file, starting from 4200 rpm, that the turbocharger clearly reaches the required pressure without any problems, then it's regulated, and after the regulation, the curves gradually diverge further."

Greetings.

[Translating...]

Aus https://community.dieselschrauber.org/en/viewtopic.php?t=26548 ergibt sich für 118kW (160PS) -> 130g/s Luftmasse.

Für 155kW (210PS, übliche Grössenordnung) wären dann 170g/s notwendig.
Mit 155g/s käme man momentan auf ca. 140kW (190PS).

Wenn Du vorher gesagt hättest, dass die Kiste getunt ist, hätte ich auch erwähnt, dass der Fehler am Datensatz liegen kann (gar nicht mal so unhäufig).

Zur Fehlersuche am besten Seriendatensatz verwenden, dann hat man eine Fehlerquelle schonmal ausgeschlossen.

Viele Grüsse, Rainer

Hello Rainer,

"As mentioned in the first post, I've already driven 10,000 km with the software optimization and haven't encountered this issue before, but you're right. It's definitely something we should rule out."

I need to talk to the tuner to see if it's possible to revert to the original software in the short term.

I created a power curve diagram immediately after the optimization using VCDS. The result was 207 horsepower. I'm not sure how to compare the engine torque values from the engine control unit with this diagram, but when you put them side by side, the values also diverge starting around 4000 rpm. The "MAF sensor" (LMM) values, which are related to engine torque, were logged in the data log.

Therefore, I'm leaning towards a stuck wastegate, which, if you can believe the search results on Google, is apparently not an uncommon issue with TSI engines.

Greetings,
Dennis.

Quote:

has already been mentioned in the first post. As described there, I have already driven 10,000 km with the software optimization

.
Possibly already forgotten by me.

The simplest and therefore most sensible thing to check right now would be to quickly remove the exhaust pipe and take a look at the wastegate.

Best regards, Rainer.

Hello everyone,

Today, I had the time and opportunity to take the troubled child to the rental workshop.
My original plan was to remove the downpipe in order to directly inspect the wastegate. Unfortunately, I have to say that I failed at this. I have no idea how to loosen the upper rear nut on the turbocharger...

Anyway, with a bit of patience, I managed to find an angle where you can clearly see the Wastegate linkage and its mounting. Using my homemade pressure pump, I applied pressure to the pressure sensor.

At approximately 0.6 bar, the rod moved smoothly and the wastegate opened; closing also seemed normal. Due to the suspicion that it might be sticking when closing, I liberally sprayed the bearings with rust remover. During the next test, and upon a sudden pressure release, a distinct metallic clicking sound could now be heard during the closing process (which was not present before).

I wasn't able to go for a log ride today, but it should be possible this weekend. I hope that solves the problem!

Greetings.

Sure, here's the translation of the text from German to English:

"Additional note from me:"

The boost pressure curve from my log today is almost identical to the others. So that wasn't the problem (unfortunately).

Hello again,

I've decided to just leave the problem alone for now. I also replaced the mass airflow sensor (MAF) with a spare part that I got at a good price, just in case.

I found through online research that these parts tend to fail around 100,000 km... So, it's a last-resort, budget-friendly option.

Since then, the error has never occurred again. The current mileage is slightly over 105,000. It might be a coincidence, or it might not. It doesn't matter anyway, the problem is gone .

Greetings.

"It's not entirely related to the topic, but last year I had a Passat AFN here that occasionally lost throttle during acceleration... meaning: according to VCDS, the throttle position suddenly went from 100% to 0% even though the pedal was fully depressed. After a certain time, it would start responding to the throttle again, until the problem repeated."

Then I discovered that a non-Bosch mass airflow sensor had been installed. After replacing it with an original part, the error disappeared.
We assumed back then that the mass airflow sensor (MAF) was drawing power, either in the form of current or voltage, from the transmission control unit (TCU).

Therefore... which brand of mass airflow sensor (MAF) was and is currently installed .

Hi,

Old: Hitachi.
New: Hitachi.

Greetings.