Key fob will not lock doors, except now it's working
 

2006 RX330 with 216K. Very nice condition.

So out of the blue, with all the doors closed and I'm standing outside of the car, when I hit the lock button on the fob, nothing happens except for a very faint beep. The locks just don't work.

I went around and opened and closed all the doors and the rear hatch. Twice. No joy. If I'm sitting in the car and hit the lock button on the armrest everything works properly. This went on for several days.

But now, out of the blue, the fob is locking the doors just fine. Doesn't anyone have an idea what might have happened?

Thanks.

Fob battery?

Seems obvious, I changed it out a year ago. I'll try another one.

But what was the faint beep?

Make sure it ins't an "off-brand" and check the date code on the package as lots are going around that are cheap and way past expiration. Yes Vincenze is likely correct definitely replace battery and check back here