NISSAN ALTIMA 2007 2.5 oxygen/AIR FUEL SENSOR LOCATION HELP?

[jez.s]

Hi Folks,

Can some one tell me how many oxygen or a/f sensor nissan altima 2007 2.5s have and where is the location of the sensor?

I can see only one upstream a/f sensor (pre cat) and cant see downstream sensor from the front of vehicle...Is my car has only one sensor or I'm missing something?

My car is showing code p 1148 & p 0031..Any help will be appreicated