I used CGDI MB tool and have some problems with a w211.
As soon as I plugged in OBD, I could not read any ezs data.
And the program stopped recognizing the device.
Serial number unknown, device not connected.
Ad first I thought that the problem what’s with my MB CGDI.
The car started good, no problems there!
After about 20 min I decided to hook up the Charger to the car. And then all was fine!
Then I figured that the car had a battery with 1 failing cell.
Still powerful enough to start many Times but lacking voltage!
So, hope this helps someone someday!
Thanks to @rob h (DK member)