I was reading a bit online where a guy had a similar problem in Germany and MB dealer replaced the EIS.

he did claim that at one point he got the thing to start by shooting the EIS with a hair dryer. How good is that I dont know, but its a free test.

He also claimed that MB pressed on the fact that the original keys need not be replaced - they will code them to the car.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)