I have seen other threads on this. I replaced the head unit that had blank screen with one from a donor vehicle. It worked for a day after I unplugged the receiver under the back seat but I only got one FM station and it said no service. When I scanned for other stations, nothing came in.
Then, I got the anti theft activated - turn ignition on and restart message. I did it several times and also exited the vehicle, locked and waited, but message is still there. Currently no sound, nav, or back up camera.
I have the donor vehicle VIN but there is no prompt to enter a radio code so I haven't tried to get the code. I have no star-xentry access.
Any suggestions?

 

You must scan for codes in the Command module.

 

I have several COMAND codes, along with many others that were there before.

 

Too many codes to research. Delete them all then check again for codes.

 

I deleted the codes and scanned again. The new report is attached. Thank You.

 

You are getting multiple codes in different modules of UNDER VOLTAGE. When you replaced the radio, did you disconnect the battery?

What is the part # of your old radio and what is the part # of the donor one?

 

Both radios are BZ9841. I did not disconnect the battery when I changed the radios, but I have had a lot of under voltage codes even before I changed the radio. I did have a bad belt about a month before I changed the radio that caused the alternator not to work and it was not charging the battery. The battery was temporarily drained of charge, but I had the belt replaced and it held charge after. It has been starting fine ever since and it was fine when I changed the radio, but I did not unhook the battery when I changed the radio. The radio worked for 24 hours before I got the antitheft message.

I thought perhaps the problem is with the misalignment of radio codes between the former unit and the donor unit in the COMAND system. I haven't seen anything on the COMAND interface on the instrument cluster about entering a code as I would have expected.

Thanks Bro,
Greg

 

All of those codes that you have stored must be deleted, then check for codes again.

Even though the W164 radio system does not require the security code entry like the W163, it recognizes that it does not belong to you vin#.

http://mercedes-benz.custhelp.com/ap...-comand-screen

 

That is what I was afraid of from the beginning. I have the VIN from the donor vehicle so I can get the radio code, but is there any way to enter the code without having the high end system like they have at the dealer?

The old radio had the blank, but slightly glowing white screen disorder. Otherwise the music played but I could not use back up camera or navigate the screens properly due to the blindness.

The other plan I thought of was to put the screen from the donor unit into the old unit and see if that works. I can buy an aftermarket high tech head unit with vastly expanded capabilities for less than I paid for the used donor head unit, but I didn't want to lose fidelity with the optical audio to the amplifier with the Harmon Kardin audio package.

Lacking a high end star system that could be my only option.

 

Did you try the fix in the PDF.

 

Yes I started the car several times and I held the power button for 10s several times too, until I heard the CD changer cycling. Same message. Should I try to unplug the radio to power it down completely? It worked for a day when I first installed it, but then I lost sound and had to unplug the amplifier to get it to network again. It worked for a few minutes and then I got the theft adtivated message that I cannot seem to get rid of.

 

You can try that but if the problem persists you will have to go M/B .

 

In Maj. Dundee's post they mention that this can happen during production as well as replacement. While it does say the units PIN is associated to the VIN of the vehicle, it says that it checks at startup through the communication network for validation. So if the COMMAND system doesn't see the communication network at startup it sets the fault.
Might I suggest you check your connections? Sounds like something might have come loose since it worked for a little bit. Maybe spray the electrical connectors with contact cleaner. Make sure the fiber connection is clean. Just a thought before you head to the dealer.

 

Thank you for the advice. I finally got it to work. I took the old, bad unit apart to see how difficult it would be to remove just the screen and swap it with the screen from the new head unit. The connector for the screen is a ribbon connector that lacks a plug. You just slide the ribbon in and terminals need to line up exactly. I wasn't sure it would work to swap it.
I put the old unit back together and saw that is was quite simple to remove and install the whole front with keypads, screen and all. Figuring the PIN was probably stored in the front somewhere, I doubted it would work, but it was so much easier than removing just the screen, so I tried it. I swapped the entire front from the new unit and old unit. I put the old unit back in the vehicle with the new front on it and it worked like a dream. It has been weeks now and still working so I think it is good.
Thank you.

 

did you take any
​​​​​Pictures...seems like a good idea.
​Trey