Octavi 2 Scout 2.0 tdi Engine cut off

Hi I am new here and wonder if someone have a idea about this Problem.

The engine works fine sometimes 60 min and sometimes 5 min before the engine cut off,when this happend

mostly its enough to wait 3-4 min and then it starts again but it will cut off again after a while.

When this happend a noticed that the engine temp gauge falls down to zero and the fan starts,and also

is not possible to conect to ECU via OBD.When the engine starts again everything is ok I can connect to ECU

but no fault codes  ( VCDS ).The Skoda workshop have so far exchanged the Power relay and the ECU unit but

its still the same problem.The told me that its probably a broken cable somewhere and it will cost a lot ( it already have )

Thanks