Mini R55 Cooper S with P420 code

[350Matt]

Hello Gents

I've got a P420 on my R55 Cooper S

I've tried cataclean a few times and sadly it doesn't seem to fix it

I clear the codes and within 300 miles its back again, I've also replaced O2 sensors to no avail

I've also used a small camera to peer inside the cat through the 1st O2 sensor hole and its not showing any melted holes but does look a little bit clogged up.



I should also say there's a fair bit of oil carry over in the inlet pipes post turbo which makes me think the cat has been poisoned by this excess oil ( probably from a worn turbo seal)



what I don't want to do is change the cat to have it pop up again because the car needs a turbo rebuild or a walnut blast



so any advice would be gratefully recieved

[ashenfie]

For sure the Oil issue must be solved first else the error will just return. Make sure there are no air leaks and both O sensors are clean and the car running temp. is ok