My 2002 LS 430 also has a fuel gauge problem. When it first occurred, it was always during cold weather and the fuel indicator would show 'empty' along with the fuel light illuminated. Once the car warmed up, you could turn it off, then back on and the fuel guage would work properly. Now it shows empty, then occasionally if you turn it off and back on it will show the fuel half full. So far, I haven't determined if it's actually half full or completely full.
Needless to say, I would love to find a solution without having to spend $600.
Thanks!
