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

Hello,

Quote:

5360 rpm, 1820.0 mbar setpoint, 1610.0 mbar actual.

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 need to see if I can do that myself before my workshop space is occupied by the caravan, otherwise I'll have to get it done by someone else.

If I manage to get it working, could I relieve the pressure on the intake side before the turbocharger and seal 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 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 the drive in those driving 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 value is highlighted when the boost pressure is at its maximum, 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 is why the boost pressure is 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 control loop. Deviations as large as the ones you're experiencing 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 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. The turbocharger can build up full pressure until the N75 valve intervenes. However, if the N75 valve closes, the wastegate remains open, and 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. Gear change --> turbine slows down --> full throttle with the wastegate valve open --> no boost pressure build-up.

Could the machine be repaired, or is a new loader needed?

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?

Good question. You should unscrew it 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 also experienced issues with those sticking before.

Best regards, Rainer.
PS: In theory, for example, the mass airflow sensor (LMM) 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), but this is less likely due to the number of potential faults.

I probably won't have any other choice. The N75 is new, so it's probably 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 correctly in the RPM ranges that showed insufficient boost pressure in the previous logs.

"I particularly notice in the log file, starting at 4200 rpm, that the turbocharger clearly reaches the required pressure without any problems, then the pressure is regulated, and after the regulation, the curves gradually diverge from each other."

Greetings.

From https://community.dieselschrauber.org/en/viewtopic.php?t=26548, we obtain 130 g/s of air mass for 118 kW (160 hp).

For a power output of 155 kW (210 horsepower, a typical range), a flow rate of 170 g/s would be required.
With a current output of approximately 155g/s, the power would be around 140kW (190 horsepower).

If you had mentioned beforehand that the box was modified, I would have also pointed out that the error might be due to the dataset (which is not uncommon).

It's best to use a standard dataset for debugging, as this eliminates one potential source of error.

Best regards, Rainer.

Hello Rainer,

"As mentioned in the first post, I've already driven 10,000 km with the software optimization and haven't encountered the error, 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 diverge further starting around 4000 rpm. The "MAF sensor" values, which are related to engine torque, are also logged in the data."

Therefore, I'm leaning towards a stuck wastegate, which, if you can believe the search results on Google, is apparently not a rare 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, I have already forgotten it.

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 I could get a very good view of the Wastegate linkage and its bearings. Using my homemade pressure pump, I then applied pressure to the pressure chamber.

At approximately 0.6 bar, the rod moved smoothly, and the wastegate opened, and the closing action also seemed normal. Due to the suspicion that it might be sticking when closing, I generously sprayed the bearings with rust remover. During the next test, and with a sudden pressure release, a distinct metallic clicking sound could now be heard when closing (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:

"Addition 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 sensor) 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, relatively inexpensive alternative.

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 be. It doesn't matter, 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 intermittently during acceleration... meaning: according to VCDS, the throttle position suddenly went from 100% to 0% while 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 initially suspected that the LMM was drawing power, either as current or voltage, from the STG.

Therefore... which brand of LMM (Linear Motion Module) was and is currently installed .

Hi,

Old: Hitachi.
New: Hitachi.

Greetings.