Hi guys I have a '02 protege5 and got a CEL which seems to be code P0421. Car idles, drives fine. Only thing I did do recently is put a chevron fuel injector cleaner in it. I just bought the car used and past inspection. Car has 107k miles. Could it just be the O2 or maybe the fuel cleaner clogged on injector and should go to a jiffy lube place and get the complete fuel system cleaning?