Mark,
Are you asking about using the Engine State to drive this output? That's my assumption, but there's not an "Idle" state for that output.
If that's what you're thinking, it seems like you could use the Get Status message to get the Engine State, map that to a tag, and then use that for a DO. The only potential issue I see is that I don't think you'll be able to get any outputs until the state is "Operational." Before then, the tagbus and mappings may not be working yet.
Hope that's helpful.
James
