This is exactly what I am hoping for.
A new Kenwood unit is going in shortly.
Don''t want to continue to have the same problem....

 

Well that eliminates thermal issues (you know I don't like being wrong!). I never had this happen, for me it was always after use and a shut down/start up like getting gas.

I have not been driving my car so I have no updates.

Peace
Bruce in Philly

 

I can't rule out multiple failure modes.

But my feel from my experience is that this is more of a power on reset error. I've never had a failure in the middle of a drive. Only at power on.

I figured it was a failing cap in the CPU reset circuit initially but when I borrowed a Durametric to reset an air bag warning light I saw a bunch of communication based errors (common in my experience when operating in a high electrical noise environment).

I then started to wonder about a software reset rather than hardware.

Now with a report that a Kenwood head unit fixes the problem it's pointing more and more to software and communication issues that could be caused by connection problems on top of caps and other things (think ... straws on a camel's back). In other words, age related degradation of the entire car as a system.

In my mind I am modeling a more robust communication protocol in the Kenwood unit that is over coming the OEM head (I recall people saying replacing the OEM head with another OEM head did not fix the problem).

But with only one anecdotal data point and a large void in knowledge, this conclusion is far from scientific!!!

 

2009 C2S. Contact Rod at https://www.caraudioinnovations.com. I purchased everything from them and did the install myself. It took a couple days but it fired right up and has worked great. I have an iphone, so especially love the wireless carpaly. I like setting my Nav destination on the phone before I leave thr house and the Kenwood connects to it as soon as I start the car. I also installled a rearview camera at the same time.

 

The only means to connect an aftermarket head unit to the Bose amp is through a MOST (stereo 2ch to optical adapter). You can buy these from a variety of sources and at all price points, but they all have the exact same generic MOST stereo-to-optical chip in them.

I have on of these and experimented with it a little to see how it might work out with an aftermarket head unit.

When the converter is powered on, it sends the turn-on command to the amplifier over the optical fiber. The MOST optical system is a two-fiber system that forms a continuous loop of send and receive optical signals.

The chip is 100% generic and I have the datasheet somewhere. One of the halmarks of the chip is that it can only send 2-channel audio over the optical fiber. You cannot "fade" front to rear or get any sound at all from the center speaker in the Bose installation. Before installing the MOST adapter, you have to set the front/rear fader on the PCM3.0 head before pulling it out. The amp will remember the setting forever and you can't adjust it on the new aftermarket head unit/MOST system at all. It doesn't matter how much you spend on it, they're all the same chip and they all work the same way.

The data from PCM-3.0 is much more complicated than the basic 2-ch audio from the MOST adapter. The data stream from the PCM3.0 can do full 5.1 channel DTS and Dolby Digital and some proprietary tricks like blending single channel voice announcements from the navigation system.

It is possible that the PCM3.0 head unit is sending corrupted audio data frames to the amplifier. It seems unlikely, but it could happen. It is also possible that the amp's optical receiver is not syncing the optical data correctly, thus producing junk audio-data internally that it is feeding to the amp section. It seems unlikely, but not outside the realm of possible.

You could try unplugging the orange MOST fiber cable at the amp when it acts up and then re-insert and see what happens.

My bet would still be on an electrolytic capacitor in the amp that's failing and causing instability and intermittent failures.

Another interesting test might be forcing a Nav-system voice announcement when the problem occurs. If you got bad audio, and then the voice came in clear, that would rule out the amplifier/power section.

 

Always good stuff Larry,

I wonder... (oh no!).... The failure frequency definitely dropped way way down when I pulled the unit and applied the thermal paste... but I wonder if it was just pulling the unit out that did it... just unplugging and plugging the connectors back in. Hmm.... Maybe I think too much.

Peace
Bruce in Philly

 

I main reason I swamped mine out for the Kenwood was the wireless Carplay. The system sounds great.

I noticed the loss of signal to the speakers always occurred when I had my iphone connected through iPad adapter. I would stop the car to get gas or something and when I restarted the car I would lose the signal. I don’t know if the ipad connection was coincidental or something bigger. That was just My experience.

 

Which head unit?

It would be nice to upgrade. I already collected all the components to retrofit an aftermarket amp under the seat too.

The PCM-3 though, has given me no reason to mess with it. It's been out of the car before, as an aftermarket system was installed it by prior owners, for certain, including a rear camera. But they put the original HU back in. Who knows, maybe mine's working great because it has been in the back of someone's closet for years instead of in the car exposed to heat and cold and weather.

I already decided that if I do replace, I'll swap the amp and the HU. Wouldn't mind removing the sub from the passenger footwell, but that would require recarpeting. (convertible has the extra hump type sub in the passenger footwell). Probably re-use the existing wiring and speaker locations and upgrade with some better cones.

But I am not touching it as long as it keeps working.

 

Kenwood Excelon DNX997XR. A little spedy but well worth it.

 

I did some homework on the MOST adapters and as Larry described, the dang things only pass front 2 channels. Even the Audison unit which is $600+ doesn't pass anything else. Why can't the dang car builders just get the hell out of the way so we can have our decent audio? All the OEM audio systems suck. I mean really suck. I should probably reserve judgement on the Mark Levinson system in the Acura R series since I haven't heard it. The Porsche audio is OK and probably acceptable given the other noise the car makes is loud and preferable... but still, once in a while we actually park it... I like the idea of the Kenwood taking the maps from the phone, that's brilliant and long overdue! All the car makers should just do that as default. Can you tell I'm a bit of an audio geek? There are so many very cool things you can do once you get the head unit channel output. DSP's are a must and there are some really nice speakers and amps out there. ARC even makes and amp with the DSP built in. Pacific Audio Products makes adapters for many car makes that will use a simple adapter to interface the OEM head unit and drop out the 4 speaker channels for external amping. Our cars are 5.1 systems so that requires more. I hope a company comes out with a multi channel MOST. It seems as soon as there are chips to do it, it will happen.

 

Yeah, there's only one chip (ever made) that does audio-to-MOST conversion and every single MOST adapter is based on it.

Some of the companies who make the MOST adapters probably do a better job of building the adapters than others. I bought a really cheap one to play with and it has a lot of ground loop noise, which it dutifully digitizes and sends it to the Bose amp. While the chips are all identical and that's 90% of the adapter, the board layout and the small amount of analog electronics make a big difference.

The optical bus is not a bad idea. The thing was supposed to allow for multiple devices, like GPS, CD changer, TV tuner, etc, all connected by the optical fiber, which eliminates ground loops and noise and in theory, simplifies the digital network wiring in the car.

But - what happened is all that stuff shrunk so fast that it is all in the head unit since about 2009 anyway. In the PCM3.0, the optical fiber is only linking the head unit to the Bose amp.

The MOST standard has moved along too. Our systems have a maximum 25mbps data rate, while the standard has evolved to over 100mbps, and I think they dropped optical in favor of copper. (could be wrong, it's been a while since I looked at the data sheet).

 

Hello, I am new to Porsche and this forum. I just bought a used 2010 Boxster that is having the same problem of the PCM cutting out. I am elated that I found this forum and I was wondering if there is a final conclusion on how to fix the problem? So far, it looks like I need to remove the Bose amp and put new heat conducting paste on it and perhaps change out the capacitors. Can you advise me from your recent experience?

 

I don't think there's been a conclusive diagnosis yet. People are experimenting.

Your dealer would probably swap the amp out. Pricey, but probably will fix it.

 

Thank you, I am inclined to try replacing the Caps since this is within my abilities as described earlier. Did anybody send you the old caps so you could test them?

 

2009 C2S 158K miles

jahb! We are looking for someone to jump ahead with this. Look back on these posts... I wrote down what the values were...Larry provided some more information.

I have an update... I had the cutout again the other night after shutting down for gas on the turnpike. This was an odd one as I was able to turn it back on after 15 minutes on the road. Usually, I have to turn the car completely off to get it to "reset". Anywho, this means squat. I am definitely getting fewer cutouts after I installed that paste, but we have evidence that thermal may not be a major factor.

I may turn to this project next week.

Peace
Bruce in Philly