this will drain the key battery.
What I do when I notice the LED is on is separate the key head and remove the battery, then press a key head button to completely drain any residual power from the tiny circuit board. Careful since the key head is apart when you push the button this will want to push the circuit board out of the key head half.
Under some conditions when the above didn't have the desired effect, I have reversed the battery and installed it for a moment. I do not know where this came from. But it appears to work, that is it gets the circuit board out of whatever goofy state it was in.
Now, I used to do the above.
But I can't recall the last time I've had to do any of the above since I stopped keeping my car keys in my pants pockets all the time. Now when I arrive at home the keys come out and go into a bowl on my dresser. At the office the keys come out and go into a bowl on my desk even before I get my coffee. The only time I keep a car key in my pocket is when I'm away from a place where I can remove my car keys and store them without fear of someone walking away with them.
Sincerely,
MarcW.