I've searched the web but cannot find what a "X1 PG" diagnostic LED would mean on a 2009/2010 LGA1366 Server Board. I've been able to determine what "PLT_RST" means and have found reference materials for it, but don't have a clue what "X1 PG" could mean. I'm thinking that "PG" portion means "Power Good" -- but do not know.
Incidently, this indicator LED burns green when the computer is running on a Macintosh Pro 2010 (12-core, two Xeon X5650s). PLEASE, even guidance to documentation that may speak on this would help.
Could you specify which specific board you have?
I checked the table for our server boards and I was unable to find the meaning of "X1 PG". If this is a Mac system, have you tried contacting Apple Support for this?