I had this problem off and on for the last 4 months and I tried different approaches to the solution. First I got the codes from my mechanic and he said I needed a new 02 sensor on the front right side. I had read about B & G sensor cleaner, so I thought I would give it a try. After a few miles the lights went out and everything seemed great. After about 5000 miles the lights came on again. I thought that if the sensor was dirty, I might try cleaning it with some rapid acceleration to blow the carbon out of the exhaust. It worked.
I have a 2003 LS430 pearl Ultra with 130,000 miles and a pleasure to drive.

 

Thanks for sharing. Sometimes you can squeeze some life out of those sensors.

In my opinion, I think its time to change those O2 sensors as eventually they will go out, and unless your planning to sell your car soon, might as well enjoy the new sensors while they are in top working order. Healthy o2 sensors will increase your gas mileage and sometimes improve engine response (but they can be a pain to replace.)