Toyota Repair: 2000 Rav 4 O2 sensor, o2 sensors, rav 4

Question
Hi ted,

I am about to replace the o2 sensor in my parents Rav 4. I see that it has 4 of them. Two before cat and 2 after. Which ones are the O2 sensor. Also i brought universal ones so i dont know what wires go where. I know that the 2 black wires are the heater wires but are unsure of the other 2. Your help is greatly appreciated

Thanks Simon

Answer
They are all O2 sensors, I would need the trouble codes to tell you which one needs to be replaced, the sensors on top are the #1 sensors and the ones on the bottom are the #2 sensors but then there is also the question which bank is it? Bank one or bank two?