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2009 E350 4Matic Wagon
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Discussion Starter #1 (Edited)
Hello all, been a member here for years but don't post much. but anyways...

I have a 2003 C240 with factory COMAND and am having problems with the AUX input cutting in/out and usually only playing through right-side speakers; acting like a loose connection would. I took it to the dealer about two years ago but they were unable to help me because there were no fault-codes and MBCPO warranty doesn't cover wiring -only hard components for the audio system- and I didn't feel like spending a million bucks to diagnose and fix something as trivial as an AUX port. They did try replacing the aux plug itself with a new one with the pigtail that connects to the main harness but this did not improve the situation.

So here's my situation now: I'd like to delve into this myself; does anybody have a wiring diagram or know what route the harness takes for the AUX? Does it go directly to the COMAND head unit or does it make stops along the way? If it does go directly to the head unit can anyone help me with a location for the plugs on the back of the head unit that correspond to the factory AUX?

My rationale is if I can cut out all the wiring between the head unit and the factory AUX port in the glovebox (I'm assuming this would be miles of wire) and wire a new 3.5mm outlet directly into the head unit, place it more conveniently in the center console, AND IT WORKS, I could forget about the factory AUX and use this new one. On the contrary, if I wire a new plug directly into the back of the head unit, AND IT DOESN'T WORK, it would prove there is a problem with the COMAND head unit and potentially warrant its replacement before my MBCPO warranty ends January 12, 2011.

Sorry for the lengthy post; I hope what I'm asking makes sense and that some of you more knowledgeable members might be able to help me out!
 

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2009 E350 4Matic Wagon
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10 Posts
Discussion Starter #2 (Edited)
Ok, looks like I found the answer to my own question. Found this on www.mercupgrades.com:

This is for COMAND 2.0
Note the pin ordering in the tables matches the layout of the connector

Comand C1 connector
1 RGB-Video Red 5 CD Changer Ground
2 RGB-Video Green 6 CD Changer +12
3 RGB-Video Blue 7 RGB V-Sync
4 RGB-Video Gnd 8 RGB Shield

Comand C2 connector
1 10 D2B Wakeup
2 TV-Audio Right 11 TV-Audio Left
3 TV-Audio Green 12 TV-Audio shield
4 Aux-Audio Right 13 Aux-Audio Left
5 Aux-Audio Ground 14 Aux-Audio Shield

6 Speed Signal 15 Reversing signal
7 CAN-B Shield 16 CAN-TV Shield
8 CAN-B LO 17 CAN-TV LO
9 CAN-B HI 18 CAN-TV HI
Looks like pins 4, 5, 13, & 14 are my guys.
 

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2009 E350 4Matic Wagon
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Discussion Starter #4 (Edited)
It is "AUX Audio shield". Or do you mean "what is a shield"? It would be the braided cable (or how are those called) that shields all other cables in a wiring harness.
I actually found, in a related article on the same site, that it's the left ground.

oh, and BTW, totally jealous of your all CDI garage...
 

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I actually found, in a related article on the same site, that it's the left ground.

oh, and BTW, totally jealous of your all CDI garage...
It should be impossible to find mistakes from Richards documents at www.mercupgrades.com. I believe both interpretations are correct. If you look at the wiring diagram, the AUX plug anyway has a common ground for L and R (no need to look at the diagram for that) but the head unit has a fourth pin that is not assigned as L ground but this pin is connected to the harness shield and to the ground point at the AUX connector.
 

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2009 E350 4Matic Wagon
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Discussion Starter #6
well... nevermind at this point. Just tore into the dash this afternoon to work on this and the effin' MB tech didn't plug the AUX lead into the harness all the way. So I did his job and the factory port works like a charm now.
 

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well... nevermind at this point. Just tore into the dash this afternoon to work on this and the effin' MB tech didn't plug the AUX lead into the harness all the way. So I did his job and the factory port works like a charm now.
Sounds like an average MB tech, unfortunately. I wish they were like the average MB tech attending this forum. The positive aspect is that this makes MB owners technically superior compared to other car owners when we have to learn to do things ourself.

Good to know you got the issue fixed.
 
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