I noticed a reply from a guy who seems to know what he's talking about. My 2003 LS400 has the same problem. If I don't drive it for a couple of weeks, the battery is dead. It's not a bad battery, I replaced the battery. There is something deraining the battery while the car is turned off. The guy who seems to know what he is talking about recommends removing the positive connection from the battery and using an ammeter (measures current) to complete the curcuit. Then you remove one fuse at a time to see the ammeter's reaction to the removal. The point here is, with the fuse removed, there won't be any current flow. Before you remove any fuses, there should be a slow drain on the battery and that will show up on your ammeter. It won't be very big, so you have to measure carefully. When you remove the fuse from the circuit that is draining your battery, your ammeter will show no current flow. Hopefully the circuit is to some unneccesary "extra" (think clock), you can just leave the fuse out, do without a clock and your fine luxury automobile, will start everytime you start it regardless of how long it sits idle. The frustrating part is, Lexus knows exactly what the problem is and they won't share it with the Lexus owner. Used car salesmen are not the only ones who cannot be trusted.
