I was thinking you need a subprogram 09001 for tool change but if the parameter is empty it seems that you do not need
did you tried another tool call?Maybe you have tool 4 already in the spindle and that is why the machine do nothing
i think for MDI comand is M06 ->Input,T01->Input
did you load all the diagnose or checked with floppy if it is corect?
diagnose from 300 to 600