My 2014 Cruze with 1.4 is running fine but we had a engine light and there’s a P0420 code. Hesitate to mess with plugs given the trouble people have with plug boots tearing. Is there a way to figure out if it’s the plugs, 02 sensor or ??? I am going to replace air filter. I disconnected the battery to check a couple things like 02 harness and now no engine light after reconnecting battery so far, but it’ll probable come back on. Anyone else deal with a 0420 code?