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PCM 2.1 keeps restarting

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The PCM (2.1) on our 2005 Cayenne S keeps restarting whilst driving. This happens when playing a CD or listening to the radio, and I noticed that sometimes when it restarts the trip computer goes to zero as well. I tried the reset code (keys 148) but that doesn't really do anything to fix it.

What is the best way to troubleshoot what is wrong with it?


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Could be a loose Most connection in the back, it would be the larger diameter Orange looking wires (actually fiber optic). The PCM's are definitely not the most reliable stereo/nav systems out there. The Audi MMI / RNS-E is a much better and more reliable system.

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Many times you will see errors from the MOST as far as lost communications with one thing or another, no CD, no Satellite radio, etc... But I have also seen restarts occur. The PCM can definitely be a finicky system, I used contact enhancer (Pro Gold) on all of my connections (Don't use on the MOST) and used clean Isopropyl Alcohol on the MOST connections and all is well most of the times. Once in a while I still get a communications error for one thing or another and I do a 1, 4, 8 reset and it will come back to normal, but most of the time it is ckay. Definitely not the most reliable system, if the reliability was better than it would be a very good system, especially when paired with a Mobridge or Dension.

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  • 4 weeks later...

An update to this:- after some troubleshooting it looks like the phone module is causing the random restarts. I took the sim card out and the problem goes away. As soon as I put the sim card back in the random restarts happen. At the time the system restarts it looks like the phone is trying to do something like initialise. Once the system is working phone calls can be made and received fine - till it restarts again.

Anyone seen this particular issue?

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I've a PCM with a Dension system fitted, for bluetooth for my iphone. Originally when I bought the car, I didnt realise the dension system was fitted, and fitted a sim chip into the PCM. Now I read the above, I recall two or three system crashes / resets in my time with the car over a year and a half period. I will remove the sim from the tray, and let you know if it ever crashes / resets again. Cheers

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  • 5 weeks later...

I've got the same problem, with the PCM rebooting every two minutes. In my case the audio cuts, the message 'Navigation not available' appears followed shortly by 'Starting Navigation' then the audio coming back on. It doesn't display the white screen Porsche logo but just momentarily loses the nav. Route guidance doesn't drop and Is still active when it comes back. Trip info seems to be correct. Phone re- initialises during this process.148 doesn't clear the problem. I'll try removing the sim card to see if that works, but I think the problem is more with the DVD player.I spoke with one of the guys at revtronic in Bradford who suggested it might be worth replacing the laser drive in the DVD..But before going down that route, does anyone have any ideas?

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  • 2 years later...

Hi, with SIM card in the tray, my phone module is restarting every few minutes ; untill I simply remove the SIM card, then it stops rebooting - so this looks like a communication problem related to the MOST ... any updates from members who have reported this here before ? How did you solve this ? Was the problem related to the MOST or to the phone module itself - or to the PCM 2.1 ?

Cayenne (MY08) GTS.

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  • 7 months later...

I have the same problem with my 2006 Cayenne basic. It has happened the first drive after a fairly long trip (400 miles). First time it went away on it's own. This time the vehicle would not start the next day. There is no SIM card in the phone.

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  • 3 years later...

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