Very familiar with JP Customs. Bought my complete TNR Nav/XM/CD upgrade for my '03 from them. I assume you've installed in your '03. The '03s do not require "programming" to play. They have the Class II databus so it's like plug-n-play. However, if it's the anti-theft lock that's preventing it from playing I would have thought JP Customs would have unlocked it before selling it to you. If it is the anti-theft lock a dealer is going to have to reset it. Is it in fact the anti-theft that's giving you the problem? If so and JP Customs can't help you try this link
Radio-Code.com