So I changed my O2 sensor about a week ago to get it ready for smog. I installed the O2 sensor and cleared the code with my scanner. I failed my smog test and the technician told me that I failed because the CEL was cleared and there was no reading, but I passed everything else. So he told me I need to drive it around for a while before I can smog it.

I drove my car for a few hundred miles to get it ready for smog again, but then I get a CEL again (p0335 and p0420). I reset the code with my obdII scanner and after about a week of driving the light came back on as expected. I plug in my scanner again expecting to see the same code, but this time its p0430.

I have no idea what to fix now. Should I attempt to change the catalyst to remedy the p0430 code even though my emissions levels were at passing levels? Seems like a big waste of money

 

I had the P0430 and put a full can of Seafoam in my tank when the tank was only half full, then when it was at empty I filled it with Shell Premium gas, the code went off on its own about 200 miles later.

A few tanks later I put in Chevron Supreme and the code came back on...
Switched back to Shell and did not have a problem with it for 3000 miles, at which point a stupid driver totaled my 3.5 ALtima.