I have a 2006 Toyota corrola and a few months ago the po171 and po300 codes come on. My car car ended up digging out almost to the point it was going to die but it made it back home. I replaced the spark plugs thinking that would be it, the code was off for awhile then came back on. I then replaced the ignition coil in cylinder 1 and the code turn d off and has been off ever since. Then a few weeks later the the code po420 came on along with the po171. So I replaced my fuel injectors and the codes went off for a few weeks. Then the po420 came back on and it’s been on ever since. Is this a sign of a bad o2sensor or could it be a bad Catalytic converter?
