Recently purchased my 2004 2500HD. I assumed the wiring was under the dash. I found where the GM harness plugs into the block but I see no harness. I am now assuming the previous owner removed the harness? My RV dealer claims the harness is fastened under the dash and all I need to do is is attach Prodigy, make the connection, and off we go.

Am I correct and need to purchase one or am I missing something?

Thanks

:welcome2: Welcome to the forum. Go back to your dealer and ask him for the harness from Prodigy that is specifically for the '03-'06 Duramax. It's only about $10 -$12, and that makes it really plug and play. By the way, you made a good choice in the Prodigy; it's a quality controller. There is some helpful info in this thread:

http://www.dieselplace.com/forum/showthread.php?t=65701