"No Codes Stored" flash will not activate until the ECU has done a test procedure of all Emissions systems and is satisfied of all relating to the Diagnostic Module
. This takes several drive cycles to complete.
[ some longer than others , depending on what is activated and needed for each test]
An added note -- A fault code has to go through a repeat process before it will trip CE, BUT, you can go back and see if the computer has picked the fault up before it gets to a stored code/CE lamp mode... This is nice when one does a repair and would like to know if fault is returning without waiting for the code to go through the time process of finally tripping CE
[ ie -- the fault has been recognized, but not enough times to CE indicate. but you can go see before-hand]

Here is a Manual from a Code Reader that happens to post Benz codes and procedures that one may find interesting info pertaining to some of these PIn locations/procedures and codes...
Will show other pin modules/codes for the Led tool...

http://www.autolib.diakom.ru:8000/CARS2/pribor/cs1000/manual/cs1000_mb.pdf