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2004 S500 4Matic
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228 Posts
Discussion Starter #1
So, I bought my S500 4Matic at 59,000 miles, now it's up to 91,000. I've had it in for service a few times and just replaced both catalytic converters at the dealership. Fortunately I have an extended warranty from Chrysler that has paid for itself, although it didn't cover the catalytic converters.

The problem I'm having is with the COMAND unit. It will occasionally power off and reset itself, or occasionally it will lose the audio or do some other wacky thing and I will have to power it off and power it on again. I'm guessing this could be a problem with the headunit or the MOST bus. My previous C240 had a similar problem.

When a headunit acts up like this, are there normally any codes stored that a service tech could pull out? I'm not sure if the error codes would be reset once the head unit is reset. I could just drive it in to the dealer and leave it in their hands. I just have no way that I know of duplicating the problem so the dealer may find nothing wrong with the head unit.

Since I have a warranty it may be worth taking it in anyway. The dealer can find out from the warranty company if the head unit is covered or not.
 

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138 Posts
Command reset etc

I've had similar problems with my 2005 S-class. I got the Merc guys to do a firmware update on the unit, which fixed the missing audio and resets, but I now have a different much more bearable problem. Sometimes the command reverts to German time. Merc's answer is to replace the command, for more money than I can buy a cheap Japanese car.............
 

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W221 & Audio Moderator
2013 S550
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10,978 Posts
Zitsky: It could be a loose fiber optic connector. If a break is occurring in the fiber optic loop, the unit will shut itself down. See the phone bulletin for your car at http://home.earthlink.net/~phdwebsite/phone_bulletins.htm for help in locating the equipment and connectors.

You could also have a malfunction in one of the components that effectively "opens" the loop, resulting in a shutdown. More often than not when that happens, you just lose audio - the whole system doesn't shut down. The W220 S-Class Encyclopedia has links for troubleshooting that.

However, when I had a similar problem with an earlier COMAND (in a '00), a firmware reload fixed the problem.

zambussi - the above won't apply to your problem - unfortunately I do not have a solution that I am confident in. You could try a system reset to factory settings, and then go back and re-enter your settings (make note of them before doing the reset).
 

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330 Posts
You should see a cascade of errors when the fibre optic loop is no longer closed, because if the loop is open at any point the whole chain cannot function. You'll see "Navigation Unavailable"..."Sound Unavailable...CD Unavailable. The loop can become open at the physical connection to a component which lets the light "escapes". Also, if any of the components themselves lose power, they can't pass the light thru so the whole system goes down, so check the power connectors as well.

Is there an aftermarket iPod module installed? If the tie in to the car's harness isn't stable you'll get that intermittent reboot problem.
 
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