Hi hello, first time asking on the forums so please bear with me. My check engine light came on and gave the code P0430 code (catalyst system efficiency below threshold bank 2) AND P0420 (Catalyst " " " Threshold Bank 1). Right now I'm trying to determine which Oxygen sensors to replace, downstream or upstream? I've been researching that upstream O2 sensors are A/F sensors while downstreams are Catalyst efficiency sensors. I know that banks are to determine whether it is right or left. So my question is are there different codes for upstream O2 sensors, if so what are the codes for upstream sensors. or is the P0430 and P0420 related to all 4 O2 sensors? Trying to pinpoint the actual problem ans which set of sensors to buy because I am pretty sure my catalytic converters are working perfectly fine, however buying a cat would be my last line of defense.
Thanks!