P013A diagnostic problem

[Crispy95]

Hi looking for advise the other day engine management light come on ethen lost power steering dropped below 10mph and it come back on so filled power steering fluid up and the engine light went off but has come back on so put an obd reader on and it shows P013A which after reading is the o2 sensor I do believe, is this an easy fix and if so where is the sensor located. Many thanks