service light

Hmm. . . I use an ODBII code reader that allows you to reset it. Been a very good investment for my ES300 '94. (First year Lexus had an ODBII port on the car). Used it several times, when the O2 was intermittent (had it changed) and when I forgot to plug in the MAF sensor cable after changing the air filter, had to reset it.

What is the cost of the ODBII code reader and where is the best place to purchase one?

You can purchase a basic OBD II Code reader for less than $100 U.S. at any auto parts store.

You will need a more sophisticated OBD II scan tool to read O2 sesnor output, voltages, etc. but these cost between 5 and 20 times more and unless you know how to interpret these readings is probably not worth the investment.