PCM 3.0 REBOOTING CONSTANTLY

[C320]

I believe that Cartronics in West Byfleet do PCM repairs in case you need someone to physically check it out.

 

[SMARTTECH]

I believe that Cartronics in West Byfleet do PCM repairs in case you need someone to physically check it out.

Spoke to them yesterday to try and find out if this was a pcm fault or just something that needed resetting, they didn't give me any info and said I would need to send it to them to be tested.

 

[SMARTTECH]

OK, getting a bit more info now.

No sound.

I would be checking the amp, wherever it is located? To me it sounds like the amp is faulty, hence the MOST network loop is now broken.

To test this you can take the MOST in and out cables out of the amp connector and hold them together, use a bit of sellotape, and see if the unit then boots up and stays on.

Also, make sure no fuses are blown, if the amp is on a different fuse to the PCM, it may have blown that will give you exactly the results you are seeing.

Took it in to the Porsche Indy yesterday and when plugged in they couldn't see any issues on the diagnostic. They tried a handover reset but the unit just didn't respond to anything. Pcm and amp fuses were checked and all fine.

When phone is connected the CarPlay side of it works via the touch screen and I can set destination on waze and it plays songs from my Spotify but you get no sound at all and the unit still keeps rebooting constantly.

Spoke to NM Automotive and they said it sounds like the HDD has failed and have suggested some tests to try before removing the unit.

 

[gizlaroc]

I don't think it is the hard drive failed. That was my first thought, but the fact you get the carplay working but no audio, makes me think the amp has failed or the fuse on the amp has blown.
You tend to get a boot loop on these if the PCM unit tries to push and over the air update, but this is more for the US market I thought, they had loads do this when a sat radio update bricked the external sat radio module and thus caused a boot loop. Even when the sat radio unit was replaced it still boot lopped as the PCM now had a corrupted file system as the update didn't complete.
Porsche pushed out a fix which required burning a new firmware onto a USB stick.

It could just be your hard drive has failed, but I would still want to rule out something on your MOST network is not at fault. I think most UK cars only have the amplifier.

When this system boots up, it talks to all the devices on the MOST network, sirrus radio, amplifier, etc. etc. If it gets no response from one of these or one of them is not powering up the network is no longer a loop, hence you do not get passed the boot logo.

I think it is fuse C10 for the amplifier.


The amp is under the drivers seat.



The easiest way to test if it is the amp, if the fuse has not blown, is remove the fibre optic connector, slide the two out of the holder and hold them together. Turn on the radio, and see if it is now boots up. If it does it is a definitely the amp.

 

[SMARTTECH]

I don't think it is the hard drive failed. That was my first thought, but the fact you get the carplay working but no audio, makes me think the amp has failed or the fuse on the amp has blown.
You tend to get a boot loop on these if the PCM unit tries to push and over the air update, but this is more for the US market I thought, they had loads do this when a sat radio update bricked the external sat radio module and thus caused a boot loop. Even when the sat radio unit was replaced it still boot lopped as the PCM now had a corrupted file system as the update didn't complete.
Porsche pushed out a fix which required burning a new firmware onto a USB stick.

It could just be your hard drive has failed, but I would still want to rule out something on your MOST network is not at fault. I think most UK cars only have the amplifier.

When this system boots up, it talks to all the devices on the MOST network, sirrus radio, amplifier, etc. etc. If it gets no response from one of these or one of them is not powering up the network is no longer a loop, hence you do not get passed the boot logo.

I think it is fuse C10 for the amplifier.


The amp is under the drivers seat.



The easiest way to test if it is the amp, if the fuse has not blown, is remove the fibre optic connector, slide the two out of the holder and hold them together. Turn on the radio, and see if it is now boots up. If it does it is a definitely the amp.

I have pulled fuses Row D fuse 9 and fuse 10 which is the pcm and the amp and left them out for 24 hours + and when putting them back in the pcm fired up with exactly the same problem.

It would be great if I could find someone who understands about the faults you get on these systems and could tell me if this is an amp or pcm fault but so far all the company's that deal with these systems have said to remove the pcm and send it off to them for testing. None of them seem interested in the amp when you explain what the fault is

 

[gizlaroc]

I would try and get your hand under the seat and see if you can get to that connector in the video with the orange MOST/optical connectors, if you unplug that, you can then slide out those two connectors and if you hold them together you have made the loop without the amp in the chain/network.

If it then boots up properly, albeit with no sound you know it is definitely the amp.

It could well be the hard drive or something else on the PCM, but you could end up with a big bill for replacement or diagnostics and be back in the same position.

If you don't have the tools to get to the amp, ask a local garage to maybe.


If you don't want to remove the fibre cables from the connector, you can buy MOST loop connectors to do it.
You simply unplug the connector from the amp and plug this into the end of the connector.

They even call them SOS fix connectors as it can help you diagnose exactly what has failed on the most network quickly by taking it out of the network.


MOST loop connector - Male and Female on Amazon Prime £5

 

[SMARTTECH]

I would try and get your hand under the seat and see if you can get to that connector in the video with the orange MOST/optical connectors, if you unplug that, you can then slide out those two connectors and if you hold them together you have made the loop without the amp in the chain/network.

If it then boots up properly, albeit with no sound you know it is definitely the amp.

It could well be the hard drive or something else on the PCM, but you could end up with a big bill for replacement or diagnostics and be back in the same position.

If you don't have the tools to get to the amp, ask a local garage to maybe.


If you don't want to remove the fibre cables from the connector, you can buy MOST loop connectors to do it.
You simply unplug the connector from the amp and plug this into the end of the connector.

They even call them SOS fix connectors as it can help you diagnose exactly what has failed on the most network quickly by taking it out of the network.


MOST loop connector - Male and Female on Amazon Prime £5

Thank you for this information, I will see if I can get to it and loop it out at the weekend as so far every company you speak to seem to want the pcm for testing and not interested in the amp. Don't want the hassle of removing it and sending away and a bill to tell me it's all fine when I can't get anyone to confirm constant rebooting is a pcm fault.

 

[gizlaroc]

I was going to say, if it is easy to slide out the PCM from the car, you can use the male most loop adpater in the back of that.
That will do the same thing in regards to testing it.

 

[Slayer]

It’s a known issue and will be the hard drive as I mentioned before. Hope it gets fixed one way or the other

 

[SMARTTECH]

It’s a known issue and will be the hard drive as I mentioned before. Hope it gets fixed one way or the other

I have ordered some most loops so I can do some further tests to confirm its not the amplifier before I remove the pcm and send off to repair

 

[SMARTTECH]

While trying to prove the fault is the pcm and not something plugged in to it I plugged my diagnostic tool in a got code 800f.
Anyone know what this means and would it cause the constant reboot I'm getting ?

 

[SMARTTECH]

After doing all the testing I can at home and the unit still rebooting constantly even with a most loop connected in the back of the pcm itself I still have the same issue So have to assume the fault is with the main unit, next is to remove and send off to have it tested and hopefully repaired.