PCM System error

[Watch-Collector]

My 987 Boxster has the above issue . The battery was disconnected for a couple of weeks and now there is no sound from the Radio , CD or multichanger . The Telephone , Navigation or Maps are now unavailable .
I have tried the `press 148 ` reset which does not fix the issue , removed fuses 9 and 10 in row D and locked/ unlocked .Nothing !
If I press Main and Trip there are exclamation marks to the left of telephone, navigation etc and the fields are blank but ticks against PCM and Software with the relevant information .
I think this is a software or similar issue as the single Cd player,, multichange and Radio all work albeit sound . The Telephone and Navigation and Maps do nothing just an error message although the Nav module does power up and I can remove the cd etc. .
What is my next step ? I think this is not a hardware fault just some sort of software re-set but how do I do it or narrow the issues down without going to PSC and more than likely get told to change an Amp or something for a huge bill ?
The Error message displays : System Error , Amplifier , navigation etc not available then it asks me to ` Confirm ` it !

Appreciate any help from the learned .

Thanks

[Richard Hamilton]

It is much more likely to be a hardware fault than software. The error message, and lack of sound, are typical of when there is a loss of communication around the fibre optic (MOST) loop. If any device in the loop fails, communications and control between the units are lost. What I find most strange is that you say the CDC is working. Are you sure about that?

[Watch-Collector]

Hi Richard , the single CD will play and I can select tracks etc but no sound . The multi changer in the front I can eject the cartridge and also put it back in it will stir into life , the same as the navigation box . Both are unavailable onscreen though .
Thanks

[Richard Hamilton]

Sounds like it could be the amp or telephone module then. I think they have separate fuses in the fuse panel, so worth checking them first. If they are OK, I would suggest getting someone with a PIWIS to do a diagnostic check, to see if it gives any clues. Happy to oblige if you are near me (Maidenhead, Berkshire).

[Watch-Collector]

Hi not sure if this helps but I did disconnect the cd changer navigation module and amp and checked the fuses in the footwell but it made no difference to the system error on screen . It would be unlucky to damage something by disconnecting the battery wouldn't it ? Would an under powered battery cause this issue at all ?
Thanks for the offer ! I might take you up on it!

[Watch-Collector]

Hi not sure if this helps but I did disconnect the cd changer navigation module and amp and checked the fuses in the footwell but it made no difference to the system error on screen . It would be unlucky to damage something by disconnecting the battery wouldn't it ? Would an under powered battery cause this issue at all ?
Thanks for the offer ! I might take you up on it!

[Watch-Collector]

Hi not sure if this helps but I did disconnect the cd changer navigation module and amp and checked the fuses in the footwell but it made no difference to the system error on screen . It would be unlucky to damage something by disconnecting the battery wouldn't it ? Would an under powered battery cause this issue at all ?
Thanks for the offer ! I might take you up on it!

[craigjm]

If this is a PCM 2.1 rather than 3.0 it sounds like being disconnected for that length of time has meant that it has lost its coding to the car and therefore the functionality is reduced. Anyone with a PEWIS or a dealer should be able to reprogramme it.

[Watch-Collector]

How do I see which version I have ? The car is a 2008 model . Thanks

[craigjm]

Watch-Collector said:

How do I see which version I have ? The car is a 2008 model . Thanks

if it has a phone keypad then its 2.1 if it doesnt then its a 3.0. A 2008 should be a 2.1

[Watch-Collector]

This is the unit I have .

[craigjm]

2.1

[Ozzie Osmond]

47 buttons!

[jakesmith]

Watch-Collector said:

My 987 Boxster has the above issue . The battery was disconnected for a couple of weeks and now there is no sound from the Radio , CD or multichanger . The Telephone , Navigation or Maps are now unavailable .
I have tried the `press 148 ` reset which does not fix the issue , removed fuses 9 and 10 in row D and locked/ unlocked .Nothing !
If I press Main and Trip there are exclamation marks to the left of telephone, navigation etc and the fields are blank but ticks against PCM and Software with the relevant information .
I think this is a software or similar issue as the single Cd player,, multichange and Radio all work albeit sound . The Telephone and Navigation and Maps do nothing just an error message although the Nav module does power up and I can remove the cd etc. .
What is my next step ? I think this is not a hardware fault just some sort of software re-set but how do I do it or narrow the issues down without going to PSC and more than likely get told to change an Amp or something for a huge bill ?
The Error message displays : System Error , Amplifier , navigation etc not available then it asks me to ` Confirm ` it !

Appreciate any help from the learned .

Thanks

Hello
This is the message you get when the MOST bus chain is not all connected up - the MOST bus is a fibre optic loop that connects all the components like amp, nav, changer, phone moduler, in series. If any component or connector fails, you get that message
Do you by any chance have a Dension or MoBridge system? As the switch on that unit causes exactly this error
If not the fault will be a hardware fault with one of the items or damage to / an unconnected the MOST connector
Why was the battery disconnected, what was happening to the car at that time for the battery to be disconnected
Is it possible (in fact likely) that one of the modules was connected as part of the work taking place when the battery was disconnected
Have you checked the connectors (the phone module is under driver seat, have you checked every fuse connected to these items on a multimeter

[Watch-Collector]

So if the telephone module goes wrong then everything packs up , no sound , and the amplifier becomes unavailable etc?
There is power to the things I stated above but I haven't tested the telephone under the seat .
Seems strange to me. The battery was disconnected as the car wasn't used for a while and it went flat !

[jakesmith]

Watch-Collector said:

So if the telephone module goes wrong then everything packs up , no sound , and the amplifier becomes unavailable etc?
There is power to the things I stated above but I haven't tested the telephone under the seat .
Seems strange to me. The battery was disconnected as the car wasn't used for a while and it went flat !

If the MOST chain is broken you get that error message
The MOST chain is fibre optic and transmits sound & has nothing to do with power to the units, the units could all be powered up but if the MOST loop is broken none of them will work
I know this as installing the Dension system involves taking the CD changer out of the loop. If you don't connect it back properly or power on the Dension system you get the message you are seeing
If power has been down for a while and nothing else has been changed, I'd say likely fault is to do with power, did you bump start the car?
Have you checked the fuse of everything in that loop? literally everything? PCM, CD changer, amplifier, phone module?
Are you sure nothing else was changed or interfered with at all?

[Watch-Collector]

There is nothing else installed its factory standard . The MOST wiring hasnt been fiddled with apart from me disconnecting the things I have already discussed.
So do I need to have it re-coded at a specialist with the diagnostics , or have the MOST wiring checked out and if so how is this done?
Thanks for all the help

[jakesmith]

It won't be a failure in the MOST cabling if that hasn't been altered, it's fibre optic and very solid
Far more likely to be a fuse knocking one of the units in the chain out, or one of the components in the chain failing when you re powered it up for some reason
So the PCM appears functional but you can't hear anything? That eliminates that which is good as it's the most expensive item. That leaves the multichanger (which appears to be working as it sounds like it is powered up), amp and phone module. No easy way to test those though without replacing with a known working one. Only other possibility I can think of is the PCM losing coding ot the car but that really shouldn't happen as coding should be written into flash memory. Sorry can't help any more but strongly urge you to go to a specialist indi garage and not Porsche who will empty your wallet rapidly for this kind of diagnostic exercise

[craigjm]

I said above that the unit has probably lost coding to the car. Take it to a Porsche specialist and they should be able to reprogramme it. Most likely issue if all parts were working normally before the battery issue.

[Watch-Collector]

I`ll give a specialist a go and see where that takes me then . I`ve checked the fuses but not yet on a multimeter which I`ll do shortly .
Thanks for all your advise much appreciated :-)