Called shop they wanted near $500 to replace the sensor. Went to local repair shop, he disconnected battery got me a new gas cap and advised to make sure you place cap on secure (like turning well past it starts clicking). Went about nine months light came on again, disconnected battery, turned cap tighter and still has not come back on.
Sensor in gas tank reports too much moisture. (forgot code) on 1998 Lexus GS300
agree with pushrod
1 more answer , 1 more comment
Did the new gas cap come from Lexus? If not, you may want to get a factory cap! Some of the aftermarket's don't hold up very well. ASSUMING that is the reason the light is back on! (?) May be something all together different this time! Really needs a scan test to be sure.
Let us know the code present. Then we might be able to help. Taking the battery loose will sometimes erase the code, but doesn't repair the problem.