Sometimes you may need to know what kind of signal you're getting to your Comcast CableBox, to help diagnose if you have some sort of problem. Maybe a loose cable, or whatnot. Here's how to do it.
Note: This is for the Comcast Digital HDTV Cable Box (Model DCH3200) (Fig-1). Most likely it will work on other models though.

To acces your Diagnostis screen start by turning your cable box off with the remote control and immediately pressing the "Ok / Select" button (Fig-2).
(Fig-3)
If you get any other status but "Good", start by rebooting your cable box (Here's how). Still the same? check all of your cable connections, particularly the coax cable and any splitters. Beyond that you'll need to call up Comcast.
Actually it is the HELP button and not OK button.

Arizona
Married
This is cool ! I never knew that was evne there !