How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Toyotatech Your Own Question
Toyotatech, Toyota Master Technician
Category: Toyota
Satisfied Customers: 71
Experience:  19 yrs experience, ASE Master Technician, Toyota Hybrid Technology certified
Type Your Toyota Question Here...
Toyotatech is online now
A new question is answered every 9 seconds

2000 Toyota Sienna: I replace an oxygen sensor

Customer Question

How do I replace an oxygen sensor in a 2000 Toyota Sienna in the rear (Bank 1, Sensor 1)?
Submitted: 9 years ago.
Category: Toyota
Expert:  OnlineMechanic replied 9 years ago.

Hello and thank you for choosing Just Answer.

Bank 1 Sensor 1 is not the rear. It's the front. Bank one is the closes to cylinder 1 which in your case is the passanger side, sensor one indicates it's the first sensor on that side. So passanger side 1st sensor (before the catalytic converter).

3(1MZ-FE) <a href=engine Firing order: 1-2-3-4-5-6 Distributorless ignition system (one coil per cylinder)" width="400" height="534"/>

It's actually very simple to replace. it's screwed into the exhaust manifold, you will need an oxygen sensor socket. Spray down the old sensor using WD-40, unhook the electrical connection and unscrew it using the socket , and extention and a rachet.

Customer: replied 9 years ago.
Should I replace the sensor after the cat. converter as well?
Expert:  Toyotatech replied 9 years ago.


I hate to over post someone else but I see that you are on line and the last expert isn't. Like he said, B1S1 is not a rear sensor (behind cat) but a front sensor (in front of cat). It is, however, in the rear most bank (nearest to the firewall - not the passenger side. It is NOT easy to access. You have to get at it from underneath the van unless you remove the entire cowl assembly that the wipers are located in. It is extremely tight under there even with a lift an some sockets won't fit. I have even had a few sensors get stuck in the manifold on the way out and had to remove the entire exhaust manifold the complete the repair. It would caution you against trying this yourself unless you are very mechanically inclined. I also wouldn't worry about the sensor behind the cat just yet. There are 3 sensors and usually once one goes, they all go, but why spend the money yet? If any of the other sensors go bad, the check engine light will come back on and you can repair as necessary. Autozone will pull the codes for free if you don't have a scanner. One last piece of advice; make sure to spend the extra money on genuine Toyota sensors; I can't tell you the number of cars that come to the shop with after market sensors that don't work. If you would like you can question a moderator here at and see if OnlineMechanic and I can split your payment when you accept because, again, I don't want to interrupt someone else's answer.

Related Toyota Questions