On 3/13/09 9:55 AM, in article
a3d9973b-3f10-4132-9459-95f76d48b955...oglegroups.com,
"waitneight@gmail.com" <waitneight@gmail.com> wrote:

> Thanks you two. The box I own to read the codes can reset them too,
> so I erased them all and the 'check engine' went off. I just drove
> for about 15 minutes and the engine light didn't come back on.
> However, I have a gut feeling that this one will come back since it
> was on for about a week...
>
> P0420 Catalyst System Efficiency Below Threshold
>
> By the way, what should I be doing about P0420 when it comes back as I
> except it shall.

I would check the downstream O2 sensor first. If it checks out, then worry
about the cat.