I am having the same exact issue. I just bought two O2 sensors since I know those cats don't usually go bad under 125K. But anyway, they were cheaper too... So have either of you had luck in fixing the problem yet?I have a 2014 Chevrolet Cruze LTZ. Its the 1.4L turbo. It has recently thrown me the P0420 code. I had the cat converter replaced at a mechanics shop due to I am over the 80,000 miles for it to be covered under warranty. Not even 3 hours later after picking it back up the check engine light comes back on. Take the car to Autozone and the diagnose it with the Same code again. I contact the mechanic and they have me bring it back to them. They look at it and everything looks and seems fine on the car. They went ahead and ordered another converter incase the one they put on had a defect in it. I took the car in Wednesday and they put the converter on again for the 2nd time. Everything seemed fine and the car was driving like brand new again. I was hopeful it was fixed. Sad to say yesterday evening the dreaded check engine light is back on. I took it back to AutoZone last night and once again for the 3rd time in a week, its the P0420 code!!