Alright you guys, my check engine light came on yesterday, I had autozone run the code and here's what it came back with. P0420 catalyst efficiency low bank 1. What exactly is this telling me? Bad CAT or bad o2 sensor? and is Bank 1 the passenger side of the vehicle? If it is the CAT i think I may be burning some oil and causong it to go bad. I just replaced the CAT on the passenger side a year and a half ago. Anyways some input would be great! Thanks guys