The amplifier for the key reception is in the center of the back window. The wires go through a rubber boot. I have had similar symptom when I would shut the tailgate suddenly my key remote world work for a bit but it hasn't worked in a couple years.

In my case I'm confident my key is dead. Needs the solder reflowed but I only have one key so can't risk until I get a replacement.

Take your key to a store that has a key tester eg home Depot that lights up when it detects the radio signal see if it lights every time you press any button

Also fix your key cylinder *yesterday* if not sooner. $10 kit on Amazon.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)