DASH LIGHT THE LIGHT ON THE DASH OF MY 1990 LEXUS LS 400 IT LOOKS LIKE A YELLOW CUP WITH A WAVE UNDER IT WHAT IS THIS?

Coolant level is low

I have the same problem. If there is coolant in the overflow tank (located to the right of the engine block towards the front as you look in with open hood), you do not have a serious problem and the car can be driven with the light on. Just check the coolant level frequently to make sure it shows in the overflow tank. The problem is the coolant level sensor has gone bad, so it is reporting inaccurately that the coolant level is low, when actually it is not low. In order to repair this you have to install a new coolant level sensor. Unfortunately, Toyota has discontinued this part for the LS 400 1991 but there is a substitute part; however this also requires replacement of the coolant over flow tank. I am trying to find a used coolant level sensor at a junk yard, but have not found one yet. LS 400 cars run forever! (Mine has 200k miles on it and going strong) The OEM new parts cost about $250 total - $95 for the new substitute coolant level sensor and about $150 for the new substitute coolant overflow tank on the online parts sites I checked.
Then you have to install them or pay to have it done.

Oil light