Lexus Rx300 Oxygen Sensor Bank 2 Sensor 1. The lexus will have a bank 1 and a bank 2 o2 sensor: The bulb part is connected to the exhaust.

This code is for the sensor before the converter on bank 2. 2000 lexus rx300 p0171 bank 1 lean and p1150 bank 2 sensor 1 malf codes shows up. S1 means the sensor is located before the catalytic converter.