Ja und genau in diesem Dokument von mir steht doch:
If display is showing A6005008, a retry can be issued by pressing the following sequence:

65 + 21 + 21+ 11

The control panel will then show C6004508. Then, it may change to A6xx500C to show the successful completion of the last command (xx=last command). After about a minute, the panel may display 01 B x (x=last IPL mode).

Now a 21 will try to force DST, if the system is not already IPLed only to DST.