I brought my car to a place to check the code for my check engine light and it came up with
po 155 b2 s1 heated o2 sensor.
I bought the part myself but have no idea where it goes, Can some one please help me.
Pictures will be most helpfull,

 

bank one is the first o2 and bank two is the second.

The first is pre cat the second is after the cat. both are screwed into the exhaust pipeing. since you have it you know what it looks like now just look at your exhaust if it is a V6 there should be one I think around where the two downpipes meet and one after the Cat. I may be wrong about the 1st one though I cant remember on the v6 but it is pre cat I know that

 

i went under the truck today and noticed there are 4 sensors and they all look the same. there are 2 on each side (drivers and pass) Does anyone know which one i need to change? the one on the drivers side or passenger and is it the one closser to the bottom of the vehicle or the one closer to the top of the vehicle?