I figured as much (coolant low), so I filled it up. But even with a full overflow bottle and radiator, the light still comes on randomly. My guess is either the sensor or it's wiring is bad.
I have the same issue on my 93 SC400. It goes off as it pleases. I've searched multiple Lexus forums to no avail.
For now I just keep an eye on the temp guage and make sure it doesnt go too high. So far it hasnt.
-LeRoy
