CayenneJIm

Been a while since i have been on the forums here. I have a Porsche Cayenne S 2004 with a PCM E1 (model BE6636) Display/Nav/ FM-AM, CD etc. ( Porsche Communication Management PCM central control unit for all infotainment).

The unit one day recently suddenly started randomly powering down (and up with key off) when I get into the car. Display fades and sometimes will still continue to play FM. Does not read Nav CD but occasionally plays music CD, Pulled the unit and sent it to a group out in CA to bench test but they told me it works fine and could not replicate the problem in the lab test harness. Reinstalled and it worked for a few hours then shut down and rebooted. Given the successful bench test it implies some kind of signaling logic sequencing problem in my harness.

Logic seems totally arcane. If I do various things like open and shut door, put in key and wait it will sometimes (rarely) power up. If I go to Accessory key position it may or may not work. Most often the display stays powered off but when driving it might suddenly power on and blare loudly. Acts like some kind of controller logic error in the power harness but some of my research indicated that it could also be due to the fiber optic ring network not finding all the devices (external CD magazine, amp, GPS nav signal etc). and getting in a race condition and shutting down without throwing up a warning message.

Some say that there's a special secret reset keypad sequence - e.g. enter 1-4-8 simultaneously and press the volume/encoder/power switch. It worked one or more times but is not a reliable method since it will often shutdown in 10 or so minutes. It acts like there's a power intermittency - some times the display will fade to barely visible but still play radio or shut down. Some times the LCD display gets all hashed out with garbage on the display or flickers. Acts possessed.

Help. Any ideas? Car is too old and high millage to warrant the cost of putting in a new unit and hoping that fixes it. It could be that its the wiring harness or auto controller module not sequencing properly - but nothing has changed as far as I know (no accidents or impacts etc). Someone said to try pulling all fuses associated with it and giving it time to bleed down signal holding capacitance and see if that clears it. Not done that yet.

How many door open/closed, door lock and key switch positions are feeding into the start up logic? Wonder if one or two of the signals is intermittent and its forcing a shut down?
Anyone have any ideas? Miss just listening to FM radio when driving around. Worried the thing will power up on its own sometimes with key off and kill my battery over night or start playing loudly and annoy neighbors.

deilenberger

Hi Jim,

2nd time tonight for this link. When wacky electrical shidt starts happening in your Cayenne - it's worth investigating: https://rennlist.com/forums/cayenne-...-moisture.html

There have been other reports of the early PCM 2, 2.1 behaving in the manner you've described. Dunno who you sent it to in California, but Becker Autosound in NJ is the authorized repair place for these beasties (the PCM is a Becker product..) What most people eventually do is replace it with a modern Android based unit - which are available from China (and a few importers) - and link with varying degrees of success to the controls of the Cayenne. The current thread on doing this is: https://rennlist.com/forums/cayenne-...l#post15568080 - doing this is likely going to be cheaper than repairing your current one, and at least you'd get maps that are in this decade for the GPS function.

BTW - the "acts possessed" is probably an apt description of the failure mode - given that - if it was mine (and I'm someone who is very comfortable around a soldering iron) - I'd be reflowing all the solder joints on the power supply portions of the boards in the PCM, and perhaps checking any capacitors for any signs of bulging which generally indicates failure. But - that's me - and I realize not everyone is up for that little chore - hence Becker Autosound. Good luck!

HTH,

CayenneJIm

Thanks so much for the reply deilenberger and the links to active Android option threads. I was hoping to just send it off for a quick "refurb" knowing that its probably an intermittent internal DC power conditioning component faillure like a leaky cap or something that used to be simple for technicians to fix. Seems the trend now is to just swap out modules with few people actually doing repairs at component level anymore. I personally don't relish the idea of digging into it myself nor reaching in with DVMs etc.and probing around on the wiring harness to see if I could detect an intermittent power input or something. My fear is that its on the CAN digital bus or the optical ring network cabling etc. or a CAN bus input signal decoder component to the PCM. Given the age/mileage of the vehicle it does sound like the easiest and most cost effective thing is to just hope its not a wiring or network problem upstream of the PCM and go try the Android. From what I have learned it sounds like with the Android I still have to splice in a power feed to the device off the harness and either live with 2 channel sound or go find a more expensive 2 channel to 4 channel converter to get the back speakers working too. Possibly also a 2:1 antenna adapter. Trying not to get into a project that takes me more than a few hours to resolve and get it all up and running again. I am about ready to just use my smartphone as my radio/music/nav player. Kind of surprised that the auto markets are not just putting in large LCD screens that can be directly networked to smartphones and presuming every one has one these days. Less stuff to go wrong and cheaper.

Thanks too for that lead to Becker. Wonder if they just have an easy exchange program to swap out old for a warrantied plug and play refurb at a fair price? These should be cheap as dirt now that they are no longer being used and just sitting in used inventory.

CayenneJIm

Just got my refurbed PCM back from Becker Autosound. Seems for the most part to be working great now. They found that the graphics subsytem was defective. Clear bright display now. Powered right up.
Forgot how cumbersome it is to set up the old CD magazine names without arrow up down keys - just the rotatory **** to scroll through the long alphabet list since all of the memory was wiped out/refreshed to factory settings.
Just happy to have basic sound for FM/AM/CD. Nav is still a little flaky. Many times it just hangs up trying to read the nav CD and the "loading nav" portion of the screen just hangs there for a long time. I noticed that as it acquired more sattelites inside my covered garage (no clear overhead sky view) it later loaded the local map. I knew GPS feeds were working fine though since my lat-long coods for location on the info screen were my home. But sometimes the thing still gives me a "can't read NAV CD" error.
Cleaned the nav CD and it helped one time before getting another message. So I burned a new CD on my PC (read it just fine) and did a raw copy of the original nav CD for my region to see if that would fix it. Not sure what the read rate technology was back then in 2004 for the original Porche PCM CD reader (I burned a new CD capable of 16x from an old ancient CD RW I found at home). It worked a few times in the PCM but would also stall out now and then on bigger Points of Interest scanning when I tested nav destination performance. Same CD plays music CDs fine though.
Hope its not a bandwidth problem internal to the old CD electronic components being out of spec on larger data reads.

Anyone know off hand what the original Porsche Nav CD reader can handle for read-speeds? I want to cut a new disk and use one at the highest read rate that the CD can reliably read in (and presume it will auto adjust based on what its max read rate is).
Not even sure they sell blank CDs for these old technology levels anymore. 16x speed CD R seems to take a fairly long time to read in regional POI data and that may be giving me "time outs".

Will tinker with it some more tomorrow and drive it around a bit. Happy overall just to have good sound again in all 4 channels.

CayenneJIm

Just a final follow up. Becker made good on the warranty rework on the Nav CD. Got it back and the whole PCM works awesome. Like new again. Getting all sentimental about the days when I first got this car and this PCM was state of the art.