b1s2 02 sensor

Thanks, I had one place tell me there is 2 sensors for that car a before and after and the dealer says 4.

There are 4, Bank 1 (cyl. 1, 3, 5, 7) sensor 1 before the cat &sensor 2 after the cat, And bank 2 (cyl. 2, 4, 6, 8) sensor 1 before the cat. & sensor 2 after the cat. There is also a cat. for each bank of cylinders.