listen, i work for a toyota dealer and any time we work on a lexus we cross reference as much as possible to get the prices down and to use our own stock, its fine.

I just looked up your es300 on our computer, p1155 is an AIR FUEL sensor code. the p1155 code is limited to california spec es300 in 98, so it is NOT an o2. the dealer probably looked up sensors for a federal spec es300 which doesnt have an a/f sensor.