I have a PCB with that MCU installed.
Since no datasheet is available an I can't see what is it like, I am willing to buy one
and replace to see if this will fix the problem.

There is only that mark on it - "Dueseldorf".
Maybe it is codename of some MCU-family...

Where is it installed?

in the right corner of PCB

it is automotive device which has only this MCU on it - other ICs are TTL - I checked them - all working.
So it is only thic IC to blame for not working...

From a device this board? Need more information to try to help you ..

Sorry for not giving complete details in previous post!
I had only PCB - it was brought to me by friend - it is from his car.
Some computer that is not working - so car is not moving at all...
Immobilizer or something ...

On PCB I described what is - this MCU and few TTLs which are OK.
Power supply 5V - OK, oscillator - running...
But board not working...