2002 C180 scanner reading P0138

[johnny679]

Hi All , my ob2 scanner picking up above code and seems a o2 sensor , ive checked underneath i have 2 , one before and after the cat , car is a 2.0 petrol , the sensoe before the cat looks easier enough but i think its the one after the cat that needs changing and wiring disappears behind the metal heatshielding and looks a right pain to change , are both sensors identicle??