When I went to the auto parts store, they say I only need 2.However with a dual exaust system, would I need four?As per scematics, they mention something about(Bank 1 sensor2, and a bank 2 sensor 2) Am I only getting half of the story??

You have 4 o2 sensors, one before the catalytic on each one and one each after. They maybe saying that just need the one after the catalytic from each side. "Bank 1 Sensor 1" is before the cat. and "Bank 1 Sensor 2" is after the cat.

I have a 94 SC400 and I am attempting to find just where they are located to determine if I can replace them myself. However, from what I have discovered I beleive I only need 2. 1996 and newer have sensors after the catalytic converter, 1995 and older do not.

Roger G.
Everett, WA