rabbit,
The Diag button doesn't behave the way you might expect or wish that it did. Under normal circumstances the diag button does virtually nothing; you press it and you get the Diag screen with the slowly spinning wheel... and that's it.
If something is *wrong* however, the Diag button will turn orange, and when you press it you will see which system is reporting an error. You can then press on that system's icon and the car will (eventually) show you a screen with the cause of the issue. As an example, the car monitors the tire pressures but under normal circumstances you cannot see them. If a tire goes out of spec (pressure too high or too low) then you can get to the Tires diagnostic page and see the pressures.
One way to easily test the diag screen is this: Start your Karma and go into "Ready" mode (when the car is ready to press "D" and drive, but leave it in Park) then get out of the Karma and take your key fob away from the car. Come back to the Karma without your key fob and you should see a Key error on the dashboard and your Diag button should now be orange letting you know there is an issue. You can then click into it.
Like some other aspects of the Command Center it suffers from from youth. Fisker Automotive wasn't around long enough to get feedback on how things are used and need to work in the real world and so much of the Command Center design is subject to a "It sounded good in the office when we designed it" problem.
Good luck!
Brent
