Looking for help. I have 2016 R Type 22k miles, the engine light came on a few times then went off now on full time. I had it diagnosed and the result was P0420 catalyst system efficiency below threshold (bank 1). I have been told likely an oxygen sensor. I understand there are 6 sensors. A few questions, 1.looking towards the car from the front (RHD)where are the sensors located relation to the part no's 2. On the diagnosis any idea which one is faulty 3. How hard are they to replace with a trolley jack ! The part no's I have looked up are front sensors C2D24756, centre right C2D54165 centre left C2D55089 rear right T2R10753 rear left T2R7732 any idea if I am right. Anybodys help would be appreciated.