Remote Access Security Key - Toyota Sienna

All of a sudden, both my remote key and my wife's remote key stopped
working on our 2001 Toyota Sienna. I replaced the batteries, but they
are both dead. These keys lok and unlock the doors, and operate the
power sliding door. I believe that there may be some way to reset the
ECU unit. But where the hell is it? where is the reset button? etc..

any help would be appreciated.

BS