They have probably just died briefly and need to be reprogramed. insert it into the ignition. If they were low enough on a charge you will likely need to drive with them in the iginition and then do the key sync process. On my 3.0 2001 model, you just insert the key, turn to the on position, remove key, press and hold unlock, press the lock button 3 times. Release both buttons at the same time on the final button press. they doors should unlock in response to the accepted programing. Press the buttons quickly but not fast, short pauses between presses seem to be the trick for me. Be sure to do your other keys immediately after to have them all programed correctly.

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2001 BMW X5 3.0 5spd Sport
-aFe Intake
-E46 Sport seat retrofit with Heat
2007 Mini Cooper S 6spd