I'm living in a north part of Switzerland and I suspect the regional delaer don't have too much experience to put the finger on the problem I have.
I had frequent lost synchronisation in the past. My ML320 '99, had a cycle of 2-3 days working, 2-3 days stopped. I mean ignition no start. Please note: the small light on the head of the anti-theft device blinks, and no error on the mileage display. With both keys. After some time, both key lost also the remote function (open/close doors). good batteries, but that's the situation. I went to the garage, and ordered a new Key from Germany + change that part where we insert the key. Working fine for 2-3 days again. Now I have 3 keys: the old keys 1&2 with, normally, no function, and the third one with good remote but start no ignition. I tried to resync., no result. The car is again to that delaer ( I have some advantages now to go there). Do YOU have some inputs? It sound very weird for me, I didn't see any similar post here...Thans a lot!

Nobody...

Try reposting in the "tech help" section.
I haven't a clue, but I hope it doesn't happen to mine!

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Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport