A4 TDI: Limp Mode Due to High Boost Pressure

Liebe Mods, ich bin hier neu und wollte eigentlich in das Eingangsforum. Leider bin ich aber jetzt hier gelandet. Kann man den Beitrag verschieben? "Thank you!"
Bitte gib mir den deutschen Text, den du übersetzt haben möchtest.

Hello everyone,

"For some time now, I've been experiencing intermittent power loss in my A4 (B5 Avant 1.9 TDI, engine AJM, manufactured in 2000, 250,000 km). The engine control unit switches to a limp mode. The error memory indicates:"

17965 P1557 035
Boost pressure control.
Limit exceeded.
sporadically.

I've already read quite a bit about it. Unfortunately, I don't have a diagnostic connector or software.

The VTG (Variable Turbine Geometry) is functioning normally, the pressure regulating valve has been replaced, and some hoses are new.

Today, I noticed that the engine also goes into emergency mode even with the hose disconnected from the VTG membrane. At 3000 RPM, you can feel a slight drop in power (you can't really talk about power when the VTG is disabled, but you can definitely feel a noticeable hesitation). Does this indicate a faulty turbocharger? Or, hopefully, just a faulty pressure sensor?

Under normal conditions, you can feel a strange vibration or rough running of the engine when you press the accelerator pedal in 4th or 5th gear, especially when demanding significant power.

I used to occasionally fill up with biodiesel some time ago. Do you think that might not be good for this type of turbo?

Do you have any other helpful tips for me? Because I'm starting to get really frustrated.

Regards - Dieseldoll

It sounds like a VTG with a stuck mechanism.

How far did he run?
Long-distance or short-distance vehicle?

Remove the turbocharger, thoroughly clean the variable geometry turbine (VGT) using machinery, and reinstall it.

It costs an apple and an egg for the gaskets and nuts if you do it yourself. I did it with my father once, and it took the whole day. Everything was disassembled and cleaned for air and exhaust! Especially the intake manifold took a lot of effort to get clean, and it didn't really have a large flow .
After that, it ran much better at speeds below 2000 RPM. Above that speed, it didn't improve, because the pressure was then normal.

Quote:

For some time now, I have been experiencing intermittent power loss in my A4 (B5 Avant 1.9 TDI, engine AJM , manufactured in 2000, 250,000 km). The engine control unit switches to a limp mode. The error memory indicates:

Before I go any further: the AJM engine has problems with almost all of its components, and there have been serious engine failures with this type of engine in the past.

Quote:

In a normal state, you feel a strange vibration or rough running of the engine when you press the accelerator pedal in the 4th or 5th gear, meaning when you are demanding real power.

Given your mileage, I suspect it's the dual-mass flywheel.

For safety's sake, check measurement block 13, 18, and 23. A PD professional can usually identify a faulty ZMS (Zero Memory System) on measurement block 013. This is the case when the cylinder quantity deviations look different after each gas pulse (e.g., before -2mg, after ,3mg on the same cylinder).

Quote:

Today, I noticed that the engine also goes into emergency mode even with the hose disconnected from the VTG membrane

.

Because of that, he has to go into emergency mode.


Possible approach: Manifold pressure sensor - in the MWB 010, the pressure readings of fields 2 and 3 should be approximately the same when the engine is not running.

Quote:

Oh yes, I thought that in this case, I could exclude the VTG

.

If the hose is disconnected and the VTG (Variable Turbine Geometry) is functioning correctly, then the valve remains open, and only a small amount of boost pressure is generated at high engine speeds. Any deviation between the target and actual values will trigger a limp-home mode.

Quote:

The VTG moves relatively slowly upwards when I connect the hose to the can while the engine is running. So, much slower than the movement downwards when I disconnect the hose.

That's also (to a certain extent) normal.

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I cannot move the VTG rod with my fingers; I can only move it with pliers or wire.

Do not underestimate the spring force of the diaphragm valve. If you disassemble it, the VTG (variable geometry turbine) should be easily adjustable by hand. However, it's not fun to remove the vacuum valve with the turbocharger installed.

Quote:

I've moved it like this at least 500 times, and I thought it was okay now.

I'm not exactly sure what the specific error code is for insufficient boost pressure, but essentially, a threshold is being exceeded. It would be interesting to see what the actual boost pressure is. If it's too low, a broken catalytic converter could be a possible cause.

Thanks in advance for your spontaneous contributions! Hmm, about the turbo, or rather the VTG (Variable Turbine Geometry)? Sometimes I get the impression that the VTG doesn't fully open smoothly when I connect the hose. I need to check that more closely.

I have two additional pieces of information:

I'm hearing a faint whistling sound at higher RPMs (although I haven't paid attention to it before). I imagine that's what a turbo whistle sounds like.

When accelerating to around 4500 RPM, there's a noticeable drop in power, somewhere between 3000 and 4000 RPM, a slight and brief dip. This is likely the point where the limp mode sometimes kicks in. So, it's not the torque reduction that starts at 3000 RPM, but rather a "dip" that wasn't there before.

"Question for VW enthusiasts: Who can read the data blocks for me? Does the dealership do it for a "small fee" (I already paid almost 30€ for just one value from the error memory)? Surely, a diagnostic test is required? Or are there any affordable hardware/software solutions for DIYers? I mean, a connector for the socket in the rear ashtray, etc. I already have a laptop. I haven't really looked at the online shops yet..."

Regards, Dieseldoll.

Good morning, gentlemen.
http://shop.dieselschrauber.de/product_info.php/products_id/46
That would be my recommendation. It also prepares you for cars you might drive in the future. Regular updates are included.
If you have to pay 30 euros each time just to read the data from the memory, the investment will quickly pay for itself, right?
In many diagnostic cases, the memory remains empty, and further analysis requires examining data blocks. If you have to go to the workshop every time, you will quickly lose a lot of money, time, and patience. Furthermore, you may overwhelm the people working there.
Buy the diagnostic system, learn how to use it, and take control of the situation yourself. Just think about how much a single, free-of-charge replacement injector pump unit can cost your household. Just as an example.

vwSchrauber wrote:

Before I go any further: the AJM engine has problems with almost all of its components, and there have been serious engine failures with this type of engine in the past.

There are definitely some who can do their job without any problems. Don't let such statements discourage you. But fundamentally, he's right, especially considering the mileage. There will always be something. And every time you ask for help here, you'll be asked to read out certain data blocks. A proper diagnostic system is essential equipment these days. It's simply not possible without it.

Hello again,

"Does anyone know how to test a pressure regulating valve? I installed a different (used) one, and the old one is here on the table with me, so I'd like to know if it still works. The coil has a resistance of approximately 16 ohms."

Regarding the sensor modules: Does my car (manufactured in 2000) have enough electronics for a diagnostic system to actually be useful?

dieseldoll wrote:

Regarding the sensor modules: Does my car (manufactured in 2000) already have enough electronics for a diagnostic system to be worthwhile?

Yes.

Steffen W wrote:

Good morning, gentlemen, http://shop.dieselschrauber.de/product_info.php/products_id/46 That would be my recommendation.

I like to start small and not jump straight into everything. Besides, I'm not really a professional hacker. Would the basic diagnostic adapter ( http://shop.dieselschrauber.de/product_info.php/products_id/36 ), with a slightly limited range of functions, be sufficient as a starting point? It's not entirely clear to me which part of the system is shareware and what limitations are associated with it. For example, the screenshots don't show the page for reading measurement blocks, but they are listed in the range of functions? And where does the upgrade for €109 lead?

Hello,

Quote:

Would a limited feature set be sufficient for getting started? It's not entirely clear to me which part of the system is shareware and what limitations are associated with it. For example, the screenshots don't show the page for reading measurement blocks, but they are listed in the feature set? And where does the €109 upgrade lead to?

It depends on what you intend to do with the system. The basic system's functionality is sufficient for reading and displaying error codes and certain measurement data blocks. Please refer to the product description for details. While this might be sufficient for older A4 models, it's not suitable for current vehicles because the interesting (displayable) measurement data blocks are located in different areas, or the respective control units are not accessible via the K-line.

The 'upgrade' from the basic system results in the semi-professional KKL system (USB).

You can find out which system is the right one for which vehicle from the following table:
http://shop.dieselschrauber.de/VCDS-Fahrzeugliste.pdf

Best regards, Rainer.

Hello everyone,

Since I hate threads that abruptly end as if the initiator has passed away, I'm here to announce the final result:

I borrowed a VAG.com tool and logged the boost pressure, intake air, etc. The boost pressure was consistently too high above 3000 RPM in 4th or 5th gear during acceleration, which caused the engine control unit to go into limp mode. I replaced all the hoses, changed the pressure sensor (not with a new one), and cleaned the VTG (variable turbine geometry). The EGR valve looked very dirty, but I didn't feel like working on it. Ultimately, I unfortunately didn't find the real cause.

It's likely that the frequent, high-speed test drives contributed to the problem, as coolant was constantly being forced out through the overflow. There was a significant amount of bubbling in the expansion tank, indicating a strong suspicion of a blown head gasket.

Now I have gotten rid of the vehicle. I bought a used 2.0 TDI Avant with 125 kw and 100,000 km, and I left my old one with the reluctant dealer. I told him what he was getting himself into .

I'm not quite satisfied with the new car yet: It takes a very long time to react after you press the accelerator. You only really notice the 170 horsepower after a while, and actually only from around 2500 RPM. I wonder if it already has a faulty turbo. However, I don't know if that might be normal for these high-performance engines.


Regards - Dieseldoll

Now I have separated myself from that vehicle. I bought a used 2.0 TDI Avant with 125 kw and 100,000 km.


I'm not yet satisfied with the new one: It takes a very long time for it to react after you press the accelerator. You only really notice the 170 horsepower after a while, and actually only from around 2500 RPM. I wonder if it already has a faulty turbo? However, I don't know if that might be normal for these high-performance engines.


From the frying pan to the fire!

If it's a Siemens product, then Mullemaus might very well be right.
A larger turbo lag is quite normal, within limits, for the 170 hp engines. The turbocharger has to handle a significantly higher pressure ratio, and a single-stage turbocharger reaches its limits there. However, if it doesn't perform as well as one would expect for 170 hp, the Piezo injectors are probably clogged again.

Regarding your predecessor model B5, I would have suspected the turbocharger pressure sensor. It's a problem that occurs just as frequently as issues with the variable geometry turbocharger (VTG) locking up.
"With your current B7 model, I suspect the problem is carbon buildup in the pre-injection nozzles (PDEs). The 2.0 4V engines build boost pressure faster than my older 1.9 engine. If that's not the case, there's likely insufficient exhaust flow. In other words, the PDEs are likely clogged with carbon. I can rule out the variable turbine geometry (VTG) turbocharger; I've never had such problems with these engines. And I've only encountered issues with the intercooler hoses on the transversely mounted engines."