mb e300 1996 speedomoter abs/ets lights on

Please note that my diesel MB E300 was taken to the local dealer and they could not find the problem of these ABS/ETS lights on.
It seems to me that they could not find the correct sensors to check.
On the other hand, and at the same time these lights were on, the speedometer acted crazy for a while and finally got stuck down the zero.
It looks like this issue turned the lights on...
Any suggestions?
Thanks in advace.

speedo gets it's information for speed from the ETS control unit. If they could not find any codes I would start with power and ground supply issues to the control unit itself. If it is the K40 relay i would just replace it. they fail a lot.