AKN 2000 Error 575: Questions & Solutions

Hi,

A6 2000 with AKN engine - performance is fine as long as it doesn't go into limp mode.
When accelerating in 3rd gear, the target pressure reaches 2065 mbar, while the actual pressure reaches 2100 mbar.

In the fourth stage, however, the pressure rises too high – it should be around 2050-2100, the same as above, but the actual pressure can reach up to 2500 mbar, and eventually, the emergency mode will be activated.

The car was driven for about half a year with a likely completely blocked crankcase ventilation system. Eventually, it started smoking from the rear when accelerating, and the pressure inside the crankcase was over 300 millibars. After replacing the ventilation system, the pressure is now at 1-2 millibars.

'Still experiencing intermittent limp mode issues. Replaced the N75 valve, checked the hoses, and inspected the turbocharger. The turbocharger's adjustment mechanism is working fully and moves very easily - it can be raised and lowered very smoothly by hand.'

Could a faulty vent, over the period that the catalytic converter was damaged, have become blocked, and therefore be causing the excessively high pressure?

If you disable the regulation (by disconnecting the N75 connector), the target pressure is approximately 2 bar, as mentioned above, while the actual pressure drops to around 1.1 bar.

Since three people have said that the only thing left to check is the turbo itself, but no one can tell me exactly what internal part of it could be broken to cause the error.

'It's easy to drive at 180 km/h if you accelerate gently. However, the emergency mode occasionally activates when you suddenly accelerate fully in the 4th, 5th, or 6th gear.'

Could you please extend the guide rod of the VTG slightly? Perhaps the guide vanes cannot open wide enough to maintain the charging pressure within the tolerance limits when the exhaust mass flow rate is high.

Hi,

If the catalytic converter were blocked, the boost pressure would not increase.
Most likely, the VTG (Variable Turbine Geometry) has become clogged with carbon deposits due to the engine's excessive blow-by caused by a faulty crankcase ventilation system.
With a little luck, taking it apart and cleaning it will be enough.
With a bit of bad luck, the wastegate might be faulty, and unfortunately, it's not available as a separate part. Also, check the vacuum system and the solenoid valve used for controlling boost pressure.

Best regards, Rainer.

Unfortunately, the disguise box might have a defect, and these are not sold individually.

Fortunately, there are always defective chargers available at E*** .

If the boost pressure is too high:
ECU retracts.
N75 should apply less vacuum pressure to the U-dose of the charger.
The spring inside the U-shaped housing should position the VTG vanes for reduced pressure.

Errors can then occur:
N75 defective.
The hose used for venting the N75 valve (which connects to the air filter) is blocked or clogged.
U-Dose is stuck.
or VTG (may be affected by heat).

Thank you for the answers - that's already a lot.

a) N75 was renewed (as I wrote).
b) A hose to the air filter - that's another idea.
c) So, I think the cylinder and spring are fine. If you adjust it either with the hand pump or manually until it's fully extended, then it retracts smoothly and evenly.
d) Setting (length) - Well, this thing is factory-set and still sealed. Once it's set, won't the length remain the same over time, and not get longer or shorter?
e) The issue with carbon buildup is another idea, but it didn't look particularly bad. After a 200km highway drive, we checked, and it was actually quite okay (after replacing the ventilation system). We also opened the EGR valve and intake manifold, but it wasn't excessively thick - just slight traces on the walls, as is probably the case with any diesel engine with 150,000 km.
f) The wave from the charger makes no noise, rotates perfectly, and has no play.

I'm going to disconnect the hose to the air filter again and blow it out with compressed air.
Small question: Does it draw air through/into the air filter box, or does it push air through/into it, during pressure relief?

Instead of speculating any longer, I would first extend the VTG shaft by a quarter or half a rotation. At what RPM do you give it full throttle?

Around 2000 RPM, the error occurs, but only at higher RPMs when you let it go up to 3800 or so... If you accelerate to 3000 RPM and then shift, it doesn't actually happen.

I suspect you're experiencing a significant torque surge during acceleration! Try connecting with VAG-COM and check for the specific torque surge codes that are occurring in your vehicle.