OK - Welcome.
Good job I have a long memory. This problem was last seen a while back...
http://forum.phathack.com/index.php/topic,747.0.htmlTurns out that the Volvo version of the Phatbox (the Volvo Digital Jukebox) actually has some slightly different data in the locations that the hack tools were checking before applying the hack. Back then, a special version was prepared which was eventually reported to have been successful. But I know that was for the very early tools, and I assume you are using a version of the modern Windows based one...?
Can you please tell us which version of hack tools you were trying to use? It may be that VorTechS, the author of the current tools needs to create a custom version for Volvo boxes - I can ask him, but it will depend on his availability.