: Code P0420

12-12-04, 12:52 PM
This is the only code i'm getting (aside from some code about the airbag). P0420 .. If i clear it, it comes back a day later. The catalytic converter is only about a year or so old. What could cause this problem? The only thing I can think of is that it started fairly soon after I did a top engine cleaner (stuff you put in the TB while engine idling and it cleans it out, makes a super nasty smell and smoke heh). Could that have toasted an oxygen sensor or something? IT says it's oxygen sensor safe.. either that or it's just a coincidence.. Anyone else seen this code and nothing else related pop up?

12-12-04, 02:35 PM
Have you tried switching to different gas? Bad gas can do this sometimes. Was the new converter an OEM or Corsa/aftermarket? Have you noticed your gas mileage going down, or has it seemed like the motor is working harder lately? It's possible either the pre- or post-converter O2 sensor is dying, but I would expect to see a code for one or the other in the very near future if that's the case. If you've had gas that had lead or sulphur in it, that can chew up a cat pretty quickly, or the new cat didn't have the same capacity or surface area that the original did perhaps. That's all I can think of at the moment.