I've found the source of the beeping. Its the VSC button, when the beeping starts if I hit the VSC button it stops. Now I just need to figure out why it stars beeping to begin with.
My 1999 LS 400 has started making very loud beeping noise, usually it happens when I go into a long curve on the Highway. Lately it does it even when driving on a straight line. Any help would be appreciated.