I have a 2002 996TT. The NAV unit has a cassette deck. Another forum suggested that all cassette-equipped NAV units are PCM version 1 and thus necessarily CD-based, not DVD-based. i.e. I can't use the later discs.

How can I tell what version PCM it is?

There is also the issue of version number of the firmware within PCM1 or PCM2. Apparently useful in determining if you can upgrade the firmware, possibly add MP3 playback. The other forum suggested that I hold down AC and the right arrow to tell but that doesn't do anything. Maybe I'm interpreting the instructions wrong. How do I determine the firmware revision?

One other thing. Part of me wants to upgrade to an aftermarket double-din NAV unit. Is there much value in the stock NAV unit that I have? Worth selling to maybe someone who is interested in keeping his 996 "stock-looking"? I'm wondering if its worth the effort to carefully remove it and sell it. The unit, combined with the Bose system, sounds quite good. If I could hack in an iPod interface, I don't know that I need to upgrade the system at all considering that Garmin Nuvi at Costco is likely worth less than a new set of Nav CDs but perform better. Any options for an iPod interface for the Nav unit?

 

You have a PCM-1, Non-MOST system. It's the easiest to replace aftermarket. Check ebay for values, but it has some.

From what I understand, even the latest disks for your Nav are from 02-03 or something like that. 2003 and up have PCM-2. Still CD based, but new disks are available. As far as I know, no 996 had a DVD based Nav.