Hi,
I just got a 2003 Lexus ES300 V6. It runs great but it failed emissions inspection. I was told that the O2 sensor B1 S1 needed to be replaced. After talking to a Lexus parts person, I became very confused.

Which O2 Sensor is B1 S1 and where is it located? My local mechanic told me to replace the one on the front manifold, but the parts guy told me that's B2. Although, the parts guy seemed confused and unsure.

Would someone be kind enough to point me in the right direction?

Thank you for your help.

a simple search would have found your answer because this queston is asked every other week.

Bank 1 is the bank of 3 cylinders closest to the firewall/windshield.

Bank 2 is the bank of 3 cylinders nearest the radiator.

Sensor 1 is the sensor up top, (between the exhaust manifold and the cat.)

Sensor 2 is the sensor down low (after the cat).

steviej

ps. get a new mechanic.

I have a 2001 Lexus ES300 with both the Check Engine Light and Trac Light on. AutoZone analysis showed code P1135 Air/Fuel sensor heater circuit malfunction. I replaced the oxygen sensor, Bank 1, Senor 1, by the radiator easily. That did not solve the problem. I tried to replace, Bank 1, Senor 2, between the firewall and engine, on the exhaust manifold. That sensor was frozen in place, seized, and could not be removed.
I went to the Lexus dealer initially and they wanted $ 162. for analysis, $ 214. for the part, and $ 216. for labor. I have 80,800 miles on the car.
Please tell me how you think I should proceed?
Thanks,
Michael A. Miller

That is because the bank by the radiator ir Bank 2. see my previous post.



If it is before the cat, that would be Sensor 1. Sensor 2 is down under the vehicle after the catalytic converter.


If you put several applications of liquid wrench on the sensor right by the threads and let it soak in over a few minutes then walk away. come back in about 30 minutes. Use a long breaker bar or put some kind of extension on your socket wrench handle leverage should get it free.