W204 model 2008 with used installed OEM command , all work but no sound

i had a problem in my original DVD unit ( Navi command unit ) and to fix it at Mercedes Agent they asked for €900, so I bought used head unit ( without the 7” screen ) because my original 7” screen works perfectly ,
after installing the new DVD /GPS head unit everything worked even the GPS , but there is no sound ,
also I can control everything from the console media Knob because non of the new command unit buttons are working!!
now , the electrician who installed it for me said it could be because the new head unit is damaged , while I suspect that I need to program my car Vin number on the new command center!
can you please advice me ABOUT what should I do ?
​​​​​​​have a good day everyone .


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MercedesMedic made a comment.
1 year 3 months ago

The sound system is not working because there is an interruption of the optical light.

There is a chance the new "used" unit needs to be programmed. There is no way of knowing for certain without pluging in a Mercedes scanner.

I would check the codes first and go from there.
Does your mechanic have Star Diagnosis?

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Rami Banbouk made a comment.
1 year 3 months ago

@mercedesmedic , Thanks a lot for fast response , as a start the problem is solved today ,
The mechanic had a diagnostic software with OBD2 but I don’t know if that is Star or another one , it could recognize my car model and it performed some start , off & reset tasks ..but that is all I know about that software!
Today I Returned the non working command and took another one from the same garage,
it worked right away with sounds and buttons ( everything),
I found out that although the two Command centers look identical but the part numbers & serials are different , one has code of Q1 and other has Q2 whatever’s that means!
Problem solved & thanks for help & attention ,
One question though , do you recommend to install. ( Mirabox or Miralink ) for iPhone morning on my OEM screen?
Please let me know through your experience if it is worth the money & efforts or if there is out there something else better , where to buy and if you have any DIY instructions!
Thanks a lot

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MercedesMedic made a comment.
1 year 3 months ago

Thanks for the update.

To be honest I haven't used wither Mirabox or Miralink. Sorry.


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