engine light bank 2 sensor

i have a 1996 mercury sable gs it a 3.0 liter 6cylinder single not the durantec i have it on a machine twice saying its the bank 2 sensor and i have bought a sensor and had my uncle put it on but we dont know where its at we went by what the mechanic told us and when i look under my hood i see 4 o2 sensors and one is on the manifold which is new and i have replaced and theres 1 behind the motor where you could reach it and the other 2 is where you have to get under the car one is located under the car in the middle of it between two pipes that spilt like a Y shape that is hard to get hard but manage to get that 1 off and replace that one and the other one is locate close to the passager side so i have 2 new co2 sensor on the car and theres 2 old one on there and i was hoping someone could tell me where the bank 2 senor is located at and if i have changed the right one. please help me..

i have a 1996 mercury sable gs it a 3.0 liter 6cylinder single not the durantec i have it on a machine twice saying its the bank 2 sensor and i have bought a sensor and had my uncle put it on but we dont know where its at we went by what the mechanic told us and when i look under my hood i see 4 o2 sensors and one is on the manifold which is new and i have replaced and theres 1 behind the motor where you could reach it and the other 2 is where you have to get under the car one is located under the car in the middle of it between two pipes that spilt like a Y shape that is hard to get hard but manage to get that 1 off and replace that one and the other one is locate close to the passager side so i have 2 new co2 sensor on the car and theres 2 old one on there and i was hoping someone could tell me where the bank 2 senor is located at and if i have changed the right one. please help me..

OK - Your engine has 2 cyl. banks. If there are 4 O2 sensors, 2 of them are on bank 2 and 2 of them are bank 1. Wherever you got the trouble code from, did they tell you bank 2 upstream or Bank 2 downstream. Upstream is the ones close to the engine.downstream are the ones under the car after the catalytic converters. I am assuming that your car has the front of the engine on the passenger side. If that is correct Bank 2 will be at the front of the car. The O2 sensor right there is Bank 2 sensor 1 (upstream). Follow the pipe that one is on and you will come to Bank 2 sensor 2 (downstream). All this said, MANY other conditions will trigger an oxygen sensor code and probably more than half of them are solved by replacing something other than the O2 sensor. Your car probably needs a proper (read Ford dealer)diagnostic and pinpoint tests to determine the real cause of the problem. Did you replace the ones you already did with Ford parts or did you go to a big box auto parts store? On emissions related components, always go to the dealer and get the right parts. Bosch parts in particular are JUNK and should never be used on a Ford - period. Were your problems diagnosed by a proper shop and not an Autozone free code check?