How many o2 sensor are on a Lexus rx 300?

The Lexus RX 300 has four oxygen sensors. Two of the oxygen sensors are located in the exhaust manifold, and two are located in the catalytic converter. The oxygen sensors in the exhaust manifold measure the amount of oxygen in the exhaust gas before it enters the catalytic converter. The oxygen sensors in the catalytic converter measure the amount of oxygen in the exhaust gas after it leaves the catalytic converter. The difference in oxygen levels between the two sets of sensors tells the engine control unit (ECU) how efficiently the catalytic converter is working.