My vehicle is a 1999 Camry (Gen4) with a V6 (1MZ-FE) engine. Mine has been in Arizona all its life, which is important because a California Camry would have feul/air sensors instead of oxygen sensors as well as other differences.
So, how many oxygen sensors does my vehicle have? Three, believe it or not. There are two "upstream" sensors. One if easily accessible front and center for the front three cylinders. The other is behind the engine near the firewall for the rear three. There is also a single "downstream" sensor after the catalytic converter.
So, which is which? And what does this Bank 1, Sensor 1 nonsense mean. Online information is contradictory - I don't think anyone has a clue.
I have the Toyota service manuals, and believe it or not, they are next to useless.
Supposedly the "Banks" refer to groups of cylinders and Bank 1 is the bank with cylinder 1.Looking at the vehicle from the front, cylinder 1 is at the left rear, i.e. passenger side near the firewall. Cylinders at the back of the engine are then all odd and 1, 3, 5 Cylinders at the front of the engine are all even and 2, 4, 6. Firing order is 123456.
Code P0141 is the same error for Bank 1, Sensor 2. P0155 is the same error for Bank2, sensor 1.
So, B1S1 would be the upstream sensor for cylinders 1,3,5 behind the engine near the firewall. B2S1 would be the upstream sensor for cylinders 2,4,6 that is handy at the front of the engine. The downstream sensor doesn't really belong to a bank, but they call is B1S2.
They guy in the link above is correct about which one is which. He used Denso part number: 234-4622. Rock Auto will sell me this for $44 (Autozone wants $104). I need to check my cable first before spending money.
Tom's Camry pages / tom@mmto.org