Electronic rear axel inoperative message
 

It's under warranty, bring it to the dealer.

I had the same thing about a 11/2 years ago twice and since it has never come back and I did nothing but restart. I've had low oil message twice also and when checked it was full so who knows what is going on with these messages sometimes???

I had this problem. Initially the same message would come up, and go away upon restart if I let the car sit for some time. Eventually the messages started to come up more frequently, and sometimes would go away upon restart but sometimes not.

I didn't notice a difference in usual driving, but in race mode taking corners fast in the canyons, the diff would not lock and it would spin just like an open diff car. Handled absolutely awful, applying throttle on corner exit with trac off or even in sport handling mode would upset the car, but again in normal street driving and even moderate speed corners it was okay. I took it to the dealer and they updated some software etc and haven't gotten the message again. Seems to work great now. Good luck

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Yes, i had this issue brought it to the dealer that changed the cables to the rear diff and never had a problem since.

Not in my case tho, i had a upgrade to my software and did not help, as i said they had to change the cabling to the diff.

Mine had that message last year, after taking it to a dealer they fixed it by securing the wire. Recently I went to another dealer for the software update as a recall and they said my diff wasn't taking the update and didn't work properly (whatever that means).
After replacing the entire differential and updating software car was amazing for a month but now I get this floating feeling in Sport plus mode, passing and changing lane last week scared the crap out of me as car went left right left right as if I was sliding.
Don't know if m diff is acting again or could it be alignment issue?

Update
 

I started getting the same error message -as everyone else- here a few months back. I ignored it at first since it happened intermittently. Usually after it rain. I finally took it in to the dealership last week. They updated the software and the car was fine for a few days. Took it out on a rainy day, put it in reverse and the error message reappeared again. The car is at the dealership now and they are ordering parts to replace the whole diff. Will update this after I get the car back to see if it occurs again.

Yeah sucks. I know what you mean. Mine was a nightmare. I posted about it in a separate thread - so as not to hijack yours. Might be one of those things where clearing the code takes care of it and it doesn't come back. Hard to say. Keep everyone posted. Always good to know what happens and the solution.

I got this message too today briefly. I think the -40 C weather here was tripping the car out :)

C63s rear diff inoperative
 

I took my car in for the same message and got it back the same day.In my case they found multiple codes in ESP Control Unit & AMG Suspension Control Unit.

They erased the faulty memory and installed a software release of AMG Suspension Control Unit.

Keeping your car for 2 weeks sounds ridiculous when other dealers are doing it same day!