I'll assume an Agilent 6890 or 7890. I think that message is displayed whenever the GC is waiting for a command to ready itself for the injection. For instance, if you're using a pressure pulse, that message will display until the vial is loaded and the instrument begins to increase the inlet pressure to perform the injection. You're basically still in split mode, and the instrument knows it needs to be splitless to start the run. There's a function somewhere in the configure screens accessible through the front panel that will allow you to turn on auto prep run - this will make the instrument ready for injection as soon as all zones hit their ready points. Otherwise, press the prep run key before every injection, assuming you're performing manual injections. If you're using Chemstation and have a sequence running, the software should advance the GC through the pre-run setpoints and you should only see this while the instrument is equilibrating at a setpoint or trying to achieve a setpoint.