I recently added a 2004 4Runner SR5 V6 w/28,000 miles to my garage, my 92' needed some company.
But the check engine light has come on already, it has been "in service" for more than 36 months so the basic warranty is up. Autozone pulled the code for me and it was PO156 Bank 2, Sensor 2 (O2 sensor). The guy there told me this should be the passenger side rear sensor (89465-60230), but after searching I found on another forum that this might actually be the code for the drivers side rear O2 sensor (89465-60220)? I already made the mistake of buying the passenger side sensor and the light came back on, so I'm assuming it was the wrong one. But I would rather not buy another one if something else is causing the code. Does anyone know for sure which sensor this code is for? I was not able to confirm anything about this code searching through old posts here on Yotatech.
Or does anyone at least know which side the #1 cylinder is on the 4.0, I couldn't find that anywhere either. That might tell me what side is Bank 1 or 2.

 

Thought I would give an update for anyone that might run into this code. I ended up replacing the rear drivers side oxygen sensor and the check engine light has not come back.

 

Bank 1 is always the bank that has #1 cylinder on it. Find out where #1 cyl is and then that would make the other side bank 2

 

Yeah, that is what I figured. But I was not able to determine cyl #1 for sure either, I have a lot to learn about the new rig I guess. But now I assume bank 2 is the drivers side, since replacing that sensor got rid of the check engine light. Oh well, at least I have 2 new O2 sensors now.

Thanks for the input.