Is there any way to get it to work without the original disk which I do not have? I tried "D", "Option+D", nothing works... I just installed Mavericks on a blank Hard Drive. Does anyone else have this problem on their 2009 Mac Pro?
You need someone with the original AHT disk to upload the following directory:
/Volumes/<name of the disk>/System/Library/CoreServices/.diagnostics - note the period before the word diagnostics
You can then copy this directory to /System/Library/CoreServices/.diagnostics on your boot disk and run diagnostics without the CD
If you have flashed your 4,1 to a 5,1, you will need the files from a 5,1 CD...
The files from the 5,1 CD can be found here:
http://www.mediafire.com/download/w7ljelef6zsjq7z/diagnostics.zip
Good luck,
JimJ
P.S. Does it sound like I ran in to this EXACT issue???? ;-)