Lexus Troubleshooting Questions? Ask a Lexus Expert
Hello and thank you for using just answer. There are 4 sensors on this car, the front 2 are air fuel ratio sensors, the 2 rear are oxygen sensors. The one you refer to is VERY VERY common to fail, it's under the car in the center exhaust pipe, the wire runs up into the cabin and it plugs in under the passenger front seat (not at all fun or easy to change).
Here's a picture of the sensor under the car :