2011 XC60 P0420 Code

Happy New year to everyone. My 2011 XC60 T6 with 150K miles threw a P0420 code, my hand OBII wouldn't clear the code so I hooked up VIDA and sure enough the ECM fault code "Catalyst System Efficiency Below threshold (bank 1)" was there. Funny enough I was not able to delete the code using VIDA, most times a failing O2 sensor will throw this code and you can clear it and then the code will come on again somewhere in the imminent future but I can't understand why I can't clear it? When I click Erase All I get a communication fault message, car not responding? I'm assuming I will have to purchase a new downstream o2 sensor but can anyone shed any light on why I cannot clear the code?

You should be able to erase a cat code. Do you live in an emission inspection required area? Before replacing your o2 or your cat - try an O2 sensor extender. Or if not needed to get a tag/registration - drive the car.

And that code DOES NOT mean your rear o2 sensor is bad.

Thanks Hoonk, I had this posting on a few sites before posting here and since I didn't get any feedback on the other sites I ordered a new sensor for less than $100. It was fun removing the old one, heating it up with a propane torch did the trick. After installing the new sensor I disconnected the battery for 10 minutes to clear the code and so far so the engine light has remained off.