I can't be sure about your exact model, but for Plasma TVs of that era, 11454 should work.  

If that doesn't send a recognized OK command, you'll probably need to test all 256 possible codes by sending EFC 00000 through 00255.  But try 00007 first, since it is the expected correct EFC.

To test, make sure the remote is in TV mode.  Tap Setup (don't hold it) and enter the 5 digit EFC.  When you enter the 5th digit the remote will send the command. Test the procedure first by sending 00207 (volume down).

When you find the correct EFC, assign it permanently using the 994 command.