V6 TDI sporadisch im Notlauf,Werkstatt möchte Lader tauschen | Posts 16+

Hi,

The control valve CANNOT exceed 100%.

It is driven by a pulsed voltage, where the duty cycle of the pulse corresponds to the specified percentage. This is a tax-related value, not a sensor reading.

The control valve converts this x% into a specific pressure ratio by "mixing" ambient pressure and vacuum - Ulf once provided a good explanation of how it works. The idea is that an iron core is suspended by the pulsed magnetic field, thereby covering or uncovering the outputs accordingly.

The resulting, controllable vacuum then controls the VTG (Variable Transmission Geometry) valve.

Errors can now be:

- The VTG is stuck - then the control would be okay, but the VTG is being moved incorrectly.
- Leaks - in that case, VTG will do something different than what the regulation "wants".
- The pressure regulating valve occasionally gets stuck - then it cannot generate the corresponding pressure based on the correct input signal.

Despite the key ratio, errors still occur because we have a control loop here: the MSG "wants" to achieve something and adjusts the key ratio. Simultaneously, the boost pressure is monitored, and if the desired effect is not achieved, the control is adjusted more aggressively (i.e., with a different throttle position).

If none of this works, it could lead to an emergency shutdown.

In your case, it's quite possible that the control valve is sticking (the iron core occasionally gets stuck), and a strong water hammer might resolve the issue.

Best regards,

Jan.

ok, thank you very much for your help. I will wait and see if the error reappears. I actually replaced another hose, and according to the workshop, it was sealed... but unfortunately, it was kinked, specifically the hose that supplies the control valve with vacuum . Maybe that was the whole problem! If not, I will have to bother you again!

If the N75 valve doesn't receive any vacuum pressure, the VTG (Variable Turbine Geometry) should operate with zero boost pressure.

Does the EDC also go into emergency mode?

(Please correct me if I misunderstood anything)

m;

... the VTG should, however, operate with zero boost pressure.
Does the EDC then also go into emergency mode???
The MSG switches to emergency mode whenever the setpoint pressure and the actual pressure deviate too much from each other, regardless of the direction of the deviation.

If the actual pressure is significantly below the target pressure (regulation limit below steps), as well as when the actual pressure is significantly below the target pressure (regulation limit above steps).

Regards,
Private.

That's why I asked under what conditions the emergency mode is activated .

CU Gremlin.

Yes, that's right... the error occurred again today, and it happened before the boost pressure built up. I'm going to replace the regulating valve just in case, since the VTG (Variable Turbine Geometry) seems to be moving too easily!

Have you ever moved the VTG (Variable Transmission Gear) using vacuum pressure?

CU Gremlin.

The VGT (variable geometry turbocharger) is working smoothly, and a new regulating valve is being installed today!

Ugh...

The question wasn't whether it was easy to operate, but whether you moved it manually or with vacuum .

Okay, so I'm going to assume that you've done both.

CU Gremlin.

Okay, so the control valve is new, but unfortunately, it hasn't made any difference. However, I've noticed something else: The limp-home mode always occurs during the build-up of boost pressure, so 'before' the turbo kicks in. The engine only goes into limp-home mode when it's cold; it never happens when it reaches operating temperature! I'm going to try removing the pressure sensor today, or does anyone have any other suggestions? Thank you.

Best regards,

Sure. Please provide the text you would like me to translate from German to English.

If the error is clearly temperature-dependent, I would NOT have replaced the valve.

Because it is independent of the engine temperature, except for some heat radiation.

However, what is completely and utterly not independent is VTG!

You haven't answered the Gremlins question yet.

And what about log files???

m;

The valve will be removed again today...

I moved the VTG using vacuum (with a syringe), and I didn't notice any sticking or anything like that. I'm going to remove the pressure sensor and check if the mechanism is possibly stiff or if the pressure sensor itself is the problem... it's easy to access on the V6!

Okay, I just removed the pressure sensor. It's unbelievable. The workshop told me the system was airtight and that the pressure sensor wasn't defective... but when I blow into it, air whistles out on the other side. While the membrane does move with enough vacuum, the pressure sensor is definitely defective! Does anyone know if these are available individually as a replacement part?

AFAIK, it's not available as a separate part, at least not officially.

Best regards, WarLord.

Hi,

There's a company (possibly called Schlueter?) that sells these cans individually. "Please look for the relevant article by Ulf; it should contain the exact name and, I believe, also the address."

Best regards,

Jan.

I read the technical article, and apparently they actually sell these parts individually, at www.turbolader.com (Schlueter). The part number that Ulf recommended for the 'upgrade' of the smaller control unit only differs by the last digit. I'll call them tomorrow to inquire. I would like to thank everyone again for their help!