Boost pressure control, regulation limit exceeded (low)

Hello everyone,

We have a VW EOS 2.0T (Bwa engine) with approximately 170,000 km on the odometer. The software was optimized around 90,000 km and has not caused any problems since then. Recently, it has lost power.
The car was running normally; the woman drove it as usual in the morning. After a short stop, it no longer had any power. At home, I read out the error code using VCDS:

P0299-02: Boost pressure control - limit below threshold.

"Errors cleared and a test drive was performed. Performance is still lacking, but the error message no longer appears. Boost pressure remains constant at approximately 1000 mbar, and the N75 valve control remains consistently at 0%. No unusual noises or smoke from the exhaust."
What have I done so far?
1) Pressure hoses checked, they are leak-tight.
2) N75 getauscht, da bei Ausbau (zur Kontrolle) beschädigt. No change.
3) Pressure applied to pressure sensor, motion detected.
4) Crankcase ventilation: OK.
5) N75 actuator diagnosis, audible clicking sound.
6) The SUV was upgraded some time ago and converted to a piston design. However, even before the upgrade, only a slightly reduced power output was noticeable.

What else could it be due to? Unfortunately, I couldn't measure the voltage from the boost pressure sensor using VCDS. I still suspect that might be the problem. I want to take another closer look at the linkage connected to the wastegate.
Do you have any more ideas?

Greetings.

Hi there,

Quote:

Charging pressure remains constant at approximately 1000 mbar

.
Behind that lies the solution to the puzzle.
But first...
- Is the turbine spinning freely?
- Is the wastegate in a closed position?
- Is the intake path clear (air filter, etc.)?

What you need to check:
- the boost pressure detected by the engine control unit (ECU) when you apply pressure to the boost pressure sensor.
- especially if nothing is coming through, check the sensor itself individually, the wiring, the output values of the main system (MSG), and potentially the MSG's reaction to a variable signal on the signal line.
You can find the pin assignments for the connector and sensor, along with the corresponding target values, in the relevant technical documentation. You might also want to search for this information within this forum.
What kind of tuning was done? Was the turbo boost control modified?
hg
Herbert.

Quote:

Charging pressure remains constant at approximately 1000 mbar

.

Hello,

absolute or relative to atmospheric pressure? I suspect you mean "no boost pressure."
In this case, first remove the air intake snorkel from the loader and check if the compressor impeller is okay or if it's loose inside.
Can you also remove the exhaust side and check if everything is okay with the turbine wheel, that the wastegate closes properly, and that the turbocharger shaft isn't broken?

Before you start troubleshooting, make sure that a charge air pipe or hose hasn't simply come loose and the turbocharger is venting to atmosphere. You usually notice this pretty quickly, but a neighbor at my old place never noticed it. At least he used his Passat to blow the leaves away from my doorstep.

Best regards, Rainer.

Ultimately, there is no boost pressure being measured; only the ambient pressure is displayed.
I checked the hoses first. They are all connected and undamaged. If there had been a small hole, the pressure would have only been slightly reduced.

How could I test a removed boost pressure sensor to see if it's functioning correctly?

What's concerning is that the magnetic valve (N75), which controls the actuator and consequently the wastegate, remains constantly at 0%.

Hi.

Quote:

Wie könnte ich denn den Ladedrucksensor ausgebaut auf Funktion prüfen?

It's extremely unlikely that it would be defective on this type (I assume it's located in the intake manifold or intercooler). If it or its wiring were electrically faulty, there would be an error code stored in the engine control unit.
If the latter doesn't exist, you can skip checking it.

With the ignition on and the engine off, the boost pressure sensor should report the same pressure as the pressure sensor in the engine control unit (ECU).
No further explanation is needed for that.

Best regards, Rainer.

Hi there,
The discussion was also taking place, or had taken place, at a different bar, with similar results.
Deswegen kam halt der Thomas zu uns.
It might be possible to figure out what trick the turbocharger pressure control system (or the tuning?) is playing on him.
It is noteworthy that, according to his report, the regulation causes the wastegate to be fully dependent on the boost pressure, which remains constant at 1000 mbar.
hg
Herbert.

I've checked again to see if the turbo is building pressure, but unfortunately, it's not. Not even a slight breeze.
A new turbo will be needed for that.

I once had a stuck wastegate on an Audi A4 2.0 TFSI.

Follow Rainer's instructions. Remove the exhaust pipe, then you can reach in with your finger. You can also check the clearance of the turbine wheel at the same time.

Regards,

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

I bought and installed a new turbocharger, and since then, the car has been running perfectly again .
At first, I couldn't see anything wrong with the rebuilt turbocharger. The shaft was rotating, not broken, the wastegate was in place and movable, and the control valve was okay. Upon closer inspection, I noticed that the turbine wheel was slightly damaged, and there were also very slight and short marks on the turbine housing. This indicated that the wheel had been stuck.

Thank you for the feedback!