check engine code indicates: either oxygen sensors or catalytic converter

[zotzic]

I have a check engine light that comes on in an '04 Aveo. The code says it is either one of the oxygen sensors or the catalytic converter. I can reset the fault and it will stay off anywhere between 50 and 200 miles. Longer trips seem to cause it come on and it seems somewhat related to the engine getting being run at highway speeds for a long time versus in town driving. Any advice or insight?

[2010AveoLT]

can we get the DTC Code in Question? because the code will be able to pinpoint a place for us to start Diagnosing your problem.

[zotzic]

The code is PO 0420 P

Thanks

[2010AveoLT]

oh dear, the Dreaded P0420: it means the Catalytic Converter is below a certain threshold for Efficiency. it could be something simple like a bad sensor, or it could be the Death Rattle of your Catalytic Converter.

[avguy]

What I would do is replace the upstream O2 sensor before messing with the much more expensive and difficult cat. Since that sensor is probably going to go anyway, not a waste of money in any case. And that does fix the P0420 some of the time as well. Please post a follow-up describing what finally fixes this for your Aveo.

[zotzic]

I also notice a service bulletin issued but I cannot get the details on SB-08-06-04-027 issued for code 0420. Anyone out there have access to the bulletin?