I have a 2000 LS, yesterday I tried starting it and there was no response. All there is is a small clicking sound. I tried jumping it and that didn't work and then I left it charging overnight and it still won't start.
I was going to go out and buy a battery and replace it myself but read here: http://wiki.answers.com/Q/Can_the_ba..._or_dealership
that you need to plug a 9 volt battery into the cigarette lighter so that the onboard computer doesn't default and blow several fuses. Is this true?

 

I've never heard that one. My suggestion is to loosen the terminals and clean them, then be sure they are tight when you replace them. If your battery is several years old, it might need to be replaced. Try to get an 800 CCA replacement in size 24F.

 

I've never heard of the 9-volt battery adapter either but if there actually is something like that I would think that it's just so the memory stuff doesn't erase. (seats, clock, etc.) When you charged the battery over night, what was the voltage when you tried it in the morning? Are you sure it's your battery that's dead and not your starter? Is it one click or alot of clicks?

 

YES ... that is why we used it in our shop, the memory stuff... and I have changed other Lexus batterys (1999) with out blowing any fuses...

 

try to jump it, if it still clicks the starter's dead.
if it starts it means you have a bad ground and/or a dead cell in the battery.

 

What is this, now you can't read either, WTF?

I tried jumping it and that didn't work

Just kiddin', ya read so much you're bound to overlook something, it happens to the best of us.
Keep up with the good advice.

 

My guess is you need a starter. You only need a battery if you test it but I doubt it.