I've having same problem for the last 9 days and knowing someone will say "we cover this already" I searched every post on remote key, tried, and miserably failed. In my case I have both of my keys not working.

To charge my key battery I made unnecessary a 60 mile trip, and leave the key in position 3 in my garage for 4 hours and nothing worked. My conclusion the battery is dead beyond repair.

Can someone give me a real solution?
I am taking this car in to a dealer Monday. If they cannot fix it, I might walk out with Lexus, or MB.
It pains my to reach the button in near the tranny shifter to get the doors for the passengers, bad example on usability.

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