I'm the recent second owner of a 2008 Cayenne S. I'm having trouble with the PCM 2.1 system. The system software is 4.1, the Nav DVD is 08.2007, Part #997.044.901.51/955.044.902.61. The PCM head unit displays an "overheat" message and turns itself off after approx. 20 seconds. When manually turned back on, it remains on with access and function to the Bose amp, cd changer and single disc player in the head. The navigation DVD player accepts the DVD mechanically, but the PCM says the DVD is not readable. I removed the Nav/DVD player and sent it to Hitech in Van Noys, Ca. where it was bench tested and no problems were found. With the player removed, the light path is open so the PCM doesn't see the amp, cd player or changer, however the Head unit stays powered on, with no "overheat" message. My dealer said "it's probably the head unit- $4700 new, $2700 refurbed". Where do you think the problem lies? (Other than dealer incompetence)