[jlmacd]

Hi. I just installed a CarPlay MMI unit in my 2014 420d Xdrive Gran Coupe F36.
To do this I disconnected the battery -ve terminal, as advised. After the installation was completed I reconnected the -ve terminal again only to be faced with the “SOS Call System Failure” warning message on the dash! I have also noticed the trip computer is no longer responding to operating the BC button ie won’t change parameter. Odometer won’t zero either from the left side dash button.

I have read through countless posts explaining about replacing the Telemetric Unit battery but I can’t see why it has just suddenly failed because the battery -ve was taken off for a few hours. Doesn’t seem logical? This message has never shown itself before this.
I am wondering if there may be a way to clear the message from the dash without unnecessarily wasting money on a new battery? Or can one just completely disable the SOS Call system as I am never likely to call upon it to use?
Will clearing this fault solve the inactivity of the Trip Computer - or is that a whole other can of worms?!

Thank you if you can assist with this.

[PETED678]

Not something I’ve come across, are you seeing any DTCs?

[LA1Z24]

It charges off the 12v battery. It's 10 years old. You removed it's charge source which allowed it's voltage to drop below a specified limit.

[jlmacd]

Which I can understand. So now it is reconnected, is it just a waiting game for it to recharge and the fault warning to disappear or does this need to be forcibly cleared from the display? Or are you saying this 10 year old battery is fubar and unlikely to recharge.
I don’t really care if it doesn’t as I will never call upon the SOS service - I just want the warning message cleared and my dash space back!

[MidtownMike]

My SOS call battery already gave up after 4 years (I don't drive the car a lot, which may have shortened it's lifespan), so I would say it's an achievement that yours held up for 10 years. Maybe the previous owner replaced it 5-6 years ago?
I have the 6WB cluster, and there the SOS Call failure notification completely blocks out the BC info area of the display, so could well be that clearing that error will reactivate your trip meter etc. Maybe someone with the same cluster as you have can comment on that, as the SOS failure is something every owner encounters at some point.

[LA1Z24]

It is not going to recharge at this point. It has fallen below a specified voltage and will need to be replaced.

[Somebloke]

Originally Posted by jlmacd

I don’t really care if it doesn’t as I will never call upon the SOS service - I just want the warning message cleared and my dash space back!

In that case you can try coding it out: https://www.6post.com/forums/showthread.php?t=1690479

[MidtownMike]

The idea of the SOS call is that it automatically contacts the emergency services when you are unconscious upsidedown in a ditch slowly bleeding out your internal organs and sends your GPS coordinates. I hope that never happens to anybody here, but coding out something like that doesn't sound smart if you can also replace the battery. When your airbags are triggered your main battery is also disconnected by a small explosive charge, and this SOS backup battery may be the only thing standing between you and a slow, lonely death.

[fe7565]

If your SOS was not updated to 4G a couple of years ago (in the US...do not know EU), it probably does not even work. 3G has been disconnected and you had to make a decision to upgrade and pay for the SOS service.

[AMG KLR]

Try leaving it alone and letting it charge up for a few days and see if it goes away, otherwise will need to replace. Mine lasted about 5 years from when car was new and I replaced it myself for 100 bucks