Strange Error Combination: Troubleshooting Guide

Hello everyone,
My car (a Passat 1.9 TDI 96kW, AWX engine with Tiptronic transmission) is currently performing terribly. It can barely reach 100 km/h on a straight road and only manages 40 km/h going uphill, and that's with the accelerator pedal fully pressed.
A year ago, I experienced the same issue, which was resolved by replacing the boost pressure sensor. However, I'm now at a loss. Several visits to VAG dealerships have yielded conflicting opinions, ranging from a clogged catalytic converter to turbocharger damage. When the error memory was read, it sometimes showed 'no errors,' and other times it displayed the following errors:
17964 P1556 035 - Boost pressure control - Intermittent fault: Regulation limit exceeded.
17978 P1570 035 Engine control unit locked.

The first mistake should have been corrected by replacing the mass airflow sensor, but it didn't work.
The second error made me very suspicious. According to the description in this technical article, my car shouldn't be able to move anymore *suspicious*.

What have I done so far?
Turbocharger pressure sensor replaced.
LMM replaced.
All accessible hoses and pipes have been checked for cracks and proper seating.

Now, I'm wondering what happens next.
Could it really be the catalytic converter? Has anyone had experience with a 'clogged catalytic converter'?
What is the actual impact of error 17978?
How can you identify a damaged or soiled VTG (Variable Torque Gear)?
What other errors should be considered?
Does anyone in the Wiesbaden area know of a reliable workshop?

I hope we can still help both of us .

Best regards from Harald in Wiesbaden.

"Well, what you need is a simple VAG COM scan and a log of the most important data, and you'd be 90% sure where the problem lies. Don't worry too much about the error code related to the engine control unit being locked. Replacing parts never solves the problem; experience has shown that. What you really need is a "desired vs. actual" value comparison, otherwise it will be difficult for us to help you here. A dirty VTG (Variable Turbine Geometry) will become noticeable through difficult adjustment. You can find information about this in the forum; just search for "VTG cleaning" and you'll find many suggestions. Otherwise, many things could be the cause, and without precise data, it's impossible to pinpoint the issue."

Have you checked the turbocharger system (intercooler, hoses, especially the connections) to ensure there are no leaks (any oil mist indicates leaks)? Is the EGR valve functioning correctly (is there any leakage in the vacuum area)?


Try to get access to a VAG COM (or something similar that logs data during driving), and the errors that have been bothering you for a year will quickly disappear, I promise!

Okay, I understand. Please provide the German text you want me to translate into English. I will only provide the translation.

Unfortunately, it doesn't really help me.
Best regards, Harald.

Quote:

Unfortunately, it doesn't really help me

.

If you don't have a VAG Com, try the following to get a general idea of where the problem lies:

Disconnect the vacuum hose from the VTg adjustment. Start the engine and, while idling, check if there is any noticeable vacuum pressure in the hose. If there is: proceed to step 2.
If that's not the case, the problem lies in the vacuum system. Either it's leaking, there isn't enough vacuum pressure, or the pressure transducer for the boost pressure is defective. An indication of a leaking system can also be seen if the shut-off valve doesn't close properly or only closes briefly when the engine is turned off. If the system seems to be leaking, reconnect everything and look for the hose that supplies the system. It's usually connected to the line from the vacuum pump to the BKV (boost control valve). Carefully disconnect it and check for leaks by blowing into the hose (it tastes delicious ).


2. - If a noticeable vacuum is present, reattach the hose while the engine is running. When doing so, pull the VTG rod all the way until it stops (approximately 10mm).

If that's the case: either the charger is faulty, or the cat is stuck. In any case, you should investigate further in that direction.
If it doesn't tighten properly or at all, even with sufficient vacuum pressure, the VTG (Variable Turbine Geometry) is likely stuck or the pressure sensor (dose) is defective.

From now on, you won't be able to proceed without diagnostic equipment.