My 08 Cayman S exhibited something like this behavior shortly after...

So, I get in the car last night, and no sound is coming out of the radio/cd player/iPod. The buttons are intermittently unresponsive (PCM 3). However, bluetooth works fine, and sound comes out from the speakers when making a call. I turned it off, let it sit until the internal short term functions were no longer available, and restarted. Same thing. Everything shows up on the console, like the station or the track that is playing, but no sound comes out. Sound from Navigation works fine. I have a durametric, and it can't connect to the PCM gateway, but it never could in the past, even in my 2006. Go out this morning, and everything is fine. All sounds coming out like they should.

Thoughts?

I bought it. The tech traced the problem to a defective sound system (radio/stereo) and it was replaced under warranty.

Before he could replace the unit, even though the car new and covered by the warranty, as per Porsche factory guidelines he used the Porsche diagnostics computer to reset the unit but the reset didn't fix things for long. The unit resumed acting up while the car was still in the service bay.

This is after the tech at the dealer where I bought the car also reset the unit. While the unit worked ok afterwards it soon started acting up again which is why I was at this 2nd dealer.

My 996's stereo can wake up -- after an engine start -- in a goofy state. All the controls appear to work but there is no sound. This behavior appears to proceed a battery failure. Before failure -- failure being the engine refused to crank -- the battery is losing power and somehow at engine start this "glitches" the radio/stereo and the goofy behavior is the result.

I had the same symptoms on my '07 S. The display lit up and seemed normal, just no sound. Volume numbers went up/down, channels changed, radio to CD, etc. Then it went away and has not returned, it's been about 6 weeks or so now.

That's all I know, though.