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PCM System error: Unknown, Unknown, Unknown...

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I just bought myself a used 2008 997.1 Carrera 3.6.

When I start the car, the PCM shows 'System error: Unknown, Unknown, Unknown...'. Please see attached image.

The radio is playing fine, the cd player is fine. I can basically access the radio, cd player, audio functions etc after I hit 'Confirm'.

I've tried the 1-4-8 reset but it does not help.

What seem to be the problem?

Help appreciated.


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Did you check if there is the right and working navi-CD inserted in the drive behind the cover in front trunk?

Please try to take the CD/DVD out and check again? Did the problem disappear? If possible, try another CD/DVD.


Greetings from Germany


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I'm guessing you do not have the Bose sound package.

It looks to me like there is a break, or bad connection, in the fibre optic (MOST) loop, which is causing a lack of communication between the varios modules (phone, navigation, etc). Seems like you are only getting the functions contained within the head unit (Radio and CD).

The reason I guess you don't have Bose, is because you are getting sound. Bose also uses the fibre optic cables for the amp, but the base system, or the ASK sound package, use the speaker outputs from the head unit.

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I checked the dvd player and it is empty. I'll have to scout for a dvd and see if it helps. Sent the car for a diagnosis and they could not find any fault; but they did mention that the error message shown is not that that they usually see with a missing dvd. Keeping my fingers crossed.

Thanks for your reply.


I do have the Bose package.

Regarding the fibre optic loop, what can I do to check for the break/bad connection you mentioned?


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Everything runs off that MOST loop. If the Most loop is broken anywhere you are going to get all kinds of warning messages in the instrument cluster. Be very careful here. The PCM in my 06 electrocuted a bunch of stuff totaling $9000 in repairs. Fortunately, car was on warranty. I ripped the PCM out and now have an Alpine Nav/head unit which is WAY better.

Edited by Mijostyn
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