Volvo V70 with Audi AEL 2.5TDI - No Power

Hello tinkerers,
A friend is having a problem with his TDI (Volvo V70, older model, year 1999)
with Audi TDI 5-cylinder, AEL, automatic, km 356000. )
If he completely removes the throttle at higher speeds and the thrust cutoff
uses ( ... shouldn't it?)
doesn't respond to further acceleration.
A bright (blue?) cloud comes out of the exhaust.
Then he briefly switches to neutral, and everything goes back to normal immediately.
It is also okay if he brings the car to a stop by releasing the accelerator pedal until
reduce speed to around 100 km/h, after which you can also accelerate again.

It started with occasional glitches at high speeds/
RPMs, now it's happening regularly even at 120 km/h.

Does anyone know what could be causing this? Engine performance and fuel consumption are okay.
My suspicion would be some kind of automation-specific regulation, which is why I have
but absolutely no experience.

Thanks for the tips,

Hello, Thomas

hello

no - does the gear remain locked and the RPM decreases slightly? should the control unit release the SSB if - until the gear no longer locks - then the idle speed is initiated (uu. is there a problem with the ESP?)

I initially thought it had something to do with automation, but the blue smoke shouldn't be harmless, right?

does he then have an error in the instrument cluster? engine light or flashing arrow? then it would simply be possible to read the error, then you would at least have a starting point.

he could basically remove the gear control unit and drive without it - then the thing would run in third gear - quite silly. maybe it could help as a test...

Greetings

Hello,
I'd like to ask if he can diagnose the problem. He can also try disconnecting the gearbox control unit, but I still need to find out where it's located. I used to have a V70TDI, but it was a manual transmission, and therefore I have no idea where the device might be.

Thank you and best regards, Thomas

The gear control unit also sits at the front of the box, where the engine control unit is located. There is space for three control boxes there, the one from the gearbox should be labeled "MSA15.7" or, as I remember, "MSA15.8" on the 99th model UU.

I also have a gear control unit from the '99 model (but MSA15.7) here, and I can provide it if needed.

Greetings