Months ago there was a post about going into the comand diagnostic mode to look at various systems. What is actually available there and how do you access the systems once you're in the diagnostic comand mode?

I know about "On cars equipped with Command, to enter the diagnostic screen
press and hold the following keys for about 8 seconds: Mute + 1 + 3"

Then what do you do? What screens are available? Can you read error codes?