VTG Error on AFN: Troubleshooting Guide

Dear fellow enthusiasts,

Now it's happened to me too - the VTG is stuck.
The new GT1749 turbocharger, installed at 175,000 km, has been working flawlessly for approximately 150,000 km.

Now, after a period of strong acceleration in third gear, the emergency mode often occurs briefly (for about 3 to 5 seconds), before it resumes accelerating normally .

I then connected my pressure gauge (the closed hose was still from my last measurements 8 years ago, located under the dashboard , and I attached it to the window using the bracket from my old navigation system ).
During the test drive, under heavy acceleration, a boost pressure of up to approximately 1.6 bar was observed, which then triggered the emergency mode after a few seconds.
Even when the system is running at full capacity, it occasionally displays a pressure of 0.2 bar (I hope it's not the pressure gauge that's faulty, but tapping on the instrument doesn't seem to improve anything...).
Bei jedem zweiten oder drittem Versuch regelt es wieder komplett sauber ein und tut so, als ob alles i. O. would be...

Now, here's my question for the experts present who I'm sure can answer it immediately:

The error memory contains only one error code.

00519 - Sensor for intake manifold pressure (G71).
28-10 - Short circuit to positive - Occasional/Sporadic.

1.) It's not that I miss him, but why isn't error code 00575 (intake manifold pressure difference) being displayed? According to the VCDS log, the pressure measured by the control unit and the pressure shown on the gauge are consistent.
Are there any temporal or logical conditions associated with the code '00575'?

'I know from another vehicle with a stuck VTG (a Skoda Octavia with 110 horsepower) that the limp-home mode can only be reset by turning off the ignition.'
Is my ECU wired differently? The 'glow coil' didn't light up here either...

Best regards, Kassen (who is already looking forward to cleaning the ATL ).

Hi Cashiers,

Your vehicle likely still has an MSA15 (028906021xx) engine control unit.

Emergency stop reset without turning the ignition on/off may cause deviations in boost pressure regulation.
100% NOT.
Your error suggests a faulty sensor within the control unit.
"Were you able to log any emergency mode events?"
Were LDR displays and recording the same thing?
Were there fluctuations in the records, or was there a fixed value (or an approximate replacement value)?

Best regards,
Micha

Hello Micha,

Thank you for the quick response.
Yes, I have the STG 028 906 021 CE installed.

According to my limited knowledge, the values of the LDA (pressure gauge) and the STG (presumably a pressure sensor or regulator) should be considered as equivalent.
The pressure gauge repeatedly reached a level of approximately 1.6 bar.

Attached is my trip log, including occasional emergency mode events.
I took notes on the MWM 03, 08, and 011 lectures. I hope that's enough.

Thank you in advance.

LG Cash Registers.

I'll check the log shortly.
I had to edit my post because I was missing a "not".
To be clear: If there's a deviation in the boost pressure regulation, the ignition must be turned off to reset the error.

Hi Micha,

Thank you for being so straightforward!
Yes, that's how I know it from the Octavia! You have to turn off the ignition in order to be able to drive with normal power again .

But maybe the log data will explain my 'limp mode light.'
The performance was definitely and noticeably reduced for a short period of time.

LG Cash Registers.

Quote:

In case of a deviation in boost pressure regulation, the ignition must be turned off to reset the error.

Bist Du sicher, dann das wäre MSA15 spezifisch. MSA12 macht das nicht. "Gas weg" is enough.
hg
Herbert.

AFN has always been MSA15 .

The boost pressure values don't appear to be anything out of the ordinary at first glance.
It's not possible. / It won't work. / Absolutely not.
Unfortunately, the actual injection amount is missing. Then we could see...
where he was actually in a sort of emergency mode.
Can you tell me the times?

Quote:

00519 - Sensor for intake manifold pressure (G71). 28-10 - Short circuit after positive voltage - Occasional/Sporadic

It means that the sensor is providing a voltage that exceeds its measurement range.
goes beyond (or at least, that's what the voltage measurement suggests).
I would now have to spend a long time searching through the software, and then maybe...
to find the value at which this error occurs.

Check in the MWB 10 to see if the ambient pressure remains constant during boost build-up, or if it also increases. A defective hose in the control unit would be a very good match for the described error pattern.

Hi Micha,

You probably mean 'times' as in the time of the 'emergency mode.'
So, in the first attempt, I encountered this situation where the LDA pressure rose to 1.6 bar at 78 seconds and then again at 83 seconds.

In these time periods, the LDA may have even indicated a pressure higher than the measured 2570 mbar. 2570 mbar is likely the measurement limit of the used 250 kPa sensor.
Driving fast while simultaneously looking at the pressure gauge is not that easy... .

I will note down the actual injection amount during the next test drive .

But the deviation from the standard pressure of 2570 millibars to 2295 millibars is quite significant, or doesn't the gas turbine tolerate this for a certain period?

LG Cash Registers.

Hello Michael (TDI-GTI-4-Motion),

The hose in the control unit is definitely leak-proof.
The hose is oily on the inside (which was to be expected), but there are no leaks.
If this hose has a leak, wouldn't that also be visible as oil mist in the control unit (STG)?

Since I have the luxury of owning a second, almost brand new STG (purchased from eblöd years ago for €50, serial number 028 906 021 JC, originally from a workshop's test and exchange pool), I will install this part today and use it for some initial test drives this week.
Unfortunately, this TCU does not have any adjustments from the administrator, but if it were the sticking VTG (which, according to your statements, is rather unlikely), then the effect I described should reappear.

I just finished the tests in MWB 011 and the basic assessment. That's exactly what you need to do next after completing the LDA.
Why is this function, which requires the engine to be running, not available during the actuator test?. Here, in the previous step, the engine is turned off, and the VTG is operated using residual vacuum...
When the ATL is cold, the rod moves smoothly back and forth without any jerking.
Tomorrow, I'll be doing it all again in the hot Atlanta weather.

If the throttle valve guide isn't stuck, meaning if the intake manifold pressure sensor (G71) is actually defective, then our administrator is correct.
https://shop.dieselschrauber.de/ladedrucksensor-250kpa-intern--p-291.php
available.

Best regards, Kassen.

Could it be that there is no surge at all, but rather a pronounced underpressure after a significant overshoot? This could indicate an air shortage, leading to a reduction in flow, and then a return to normal.

Hello fellow enthusiasts,

Here's a quick update.

This morning, while at a traffic light, I noticed on my LDA (pressure gauge) that I still had approximately 0.2 bar of boost pressure for a short time, even with the engine turned off. The pressure then drops irregularly to around 0 bar. The pressure gauge is working correctly; there's no stuck needle...

With that, I have a perpetual motion machine with 4 rings .
or
a blocked hose from the pressure pipe to the control unit (STG), where I also tap into the LDA.
Unfortunately, the latter turned out to be the case .

The nearly closed hose essentially stored the pressure (my gauge and the hose act as an additional storage volume).
Since this hose is actually a thin PA pipe and runs almost perpendicularly into the water tank along with several thick cables within a rubber grommet, I suspect that there's a kink forming here. I certainly won't cut the rubber grommet to replace the pipe.
Instead, I installed a 3.5 mm hose as a bypass and connected it to the waterproof cable gland on the black water protection housing of the inverter.

What immediately caught my attention during the test drive was that the LDA indicator is now flickering again. Previously, it was being filtered out by the narrow opening (low-pass filter).
During this test drive, I immediately encountered error code 00575 with the correct limp-home mode engaged.
The search is therefore not over yet.
I then tested the variable turbine geometry (VTG) immediately while the engine was still hot (using diagnostic data 011 and basic settings). Everything was fine – the rod moved quickly and smoothly back and forth.

With that, I'm now slowly reaching the end of my (limited) knowledge .

Attached is the log file from the trip with (a real) emergency mode and error code 00575.
To me, it looks like a stuck VTG (Variable Transmission Gear), because despite a 95% duty cycle, the pressure isn't decreasing. And after about seven seconds, the emergency mode kicks in (constantly at 92.4% duty cycle = ATL set to 'forward').
Perhaps someone will take pity and look at the data.
Thank you in advance.

@guste100: That could very likely be the explanation for my 'Light' emergency mode. The blockage in the pipe probably cleared due to high pressure, and then the control system (STG) significantly reduced power output.

Best regards, Kassen.

Hi,

If, when using the default setting mode, the VTG (Variable Geometry Turbine) immediately pops into the other position upon opening, it indicates that the ventilation system is free from any vacuum pressure.
Has anything been adjusted or loosened on the VTG rod, such as the locking nut?
You can then assume that the VTG (vacuum train control) is stiff or stuck at a certain point. When the vacuum cylinder is disconnected, you should be able to move the VTG lever freely without any noticeable resistance.
The distance from the edge to the VTG (Vertical Turning Gauge) when it's in the "up" position is approximately 1 cm.

See:
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Best regards, Rainer.

Hello Rainer,

It's definitely not been screwed onto the VTG bar. The original sealant is still present on the lock nut.

I will take a closer look at the ATL.

What you naturally can't see with the default viewing angle (since the laptop is on the passenger seat...) is whether the rod immediately goes down when ventilation is activated. You can't hear the 'plop' sound when the engine is running...

I will simply connect my vacuum gauge in parallel to it.

I'm already preparing to verschandeln the ATL (by getting screws, seals, and a cutting ring).

Does the ATL itself also require parts (new nuts, seals)? Where can one likely find these special parts that are heat-resistant?
I couldn't find any information in the attached article.

Best regards, Kassen.

Quote:

What you naturally can't see with the default view (since the laptop is on the passenger seat...), is whether the rod immediately goes down when ventilation is activated. You can't hear the "plop" sound when the engine is running...

Lappi does that all by himself repeatedly until it breaks down; why don't you just go forward and see what's happening?
The engine can run during this process, and it must do so if not all of the vacuum is to be created.

Best regards, Rainer.