Hello all.
I have looked on this site and the other 2 sites that tend to be popular and I think that I have an answer to a problem but would like to ask it straight up to be sure.

I recently sold a PCM2.1 unit, the DVD unit, and assorted parts including harnesses and antenna and NAV software to a person that is driving a 2006 Cayman. The installation I think was being done personally and not by the dealer.
The user tells me that the PCM comes on, takes in CDs and ejects them but that there is no image on screen at all. What could be the problem?
After what I have been reading of retro-fit installations, the users should and often need to go to the dealer to activate the unit so that the OBC can 'see' the PCM.
What I am looking for is some form of hard evidence to pass along to troubleshoot to minimize the troubleshooting of this unit.
Would a blown fuse cause this? I don't know yet if the user unplugged the battery prior to installation and if that would cause an issue or not. If the fuse in the back of the PCM would blow, what would be the result?
Would a bad fiber cable be the cause?

Any absolute answers would be great. Thanks.