The fuel gauge on my '06 LX470 has started to fluctuate and not reflect the actual amount of fuel in my tank. At start up, the fuel gauge may read correctly 3/4 of tank, then a short time later, read 1/2 or less. While driving I can at times see the fuel gauge moving up or down. I've got no fault codes or issues with air fuel mixture per my ThinkDiag scanner. Any thoughts on what might be at issue or what to check on my scanner? I'm using ThinkCar's Toyota/Lexus software and their ThinkDiag bluetooth scanner. My service records do not indicate any replacement of the fuel pump. Appreciate any feedback.