Confused Between Air Fuel Ratio Senor And Upstream Oxygen Sensor

[Nykaz]

Hi,

Recently, my car's CEL is up.(1998 Lexus ES300) Went to a shop, tested out it was the P1135 and P1155 code. B1S1 and B2S1

The dealer told me it is the upstream oxygen sensor. However, the price is expensive for me. So I decided to buy one for local auto parts store or online.

Then I find out someone said B1S1 and B2S1 suppose to be Air Fuel Ratio Sensor instead of oxygen Sensor.

My questions are:

1. Is Air Fuel Ratio sensor the same as Upstream oxygen sensor?

2. Which One should I buy to repair my car?

[lexis lexus]

_{AF sensor is different than the o2 sensor. Using different technology to do the same thing, i.e. measure 02 content of the exhaust gas. toyota/lexus switched over in '98. Generally, I think of these things like expensive spark plugs, as they wear out and need to be replaced every 100k or so. You may want to try looking on Rock Auto, and I've heard some folx have bought them on amazon.}

_LL