O2 sensor location

Depends on what car/truck you have. They are normally before the catalytic converter (in between cats and exhaust manifold) and after the catalytic converter, on both sides of the exhaust. Bank one is normally the driver side and bank two is the left. Most cars keep with that however they are different for in-line 4cly. 4cly normally have a catalytic converter and exhaust manifold combined as one and the o2 is typically on the top and that system. Front wheel drive v6 does a similar set up, and they are a pain in the rear end to do anything with, they o2 are on both sides since it has two exhaust ports. Hope that helped!

*add to ^^* some cars have 3 cats and will have an o2 in between they two in- line catalytic converters