I originally had a ses light which turned out to be a 0443, meaning there was an issue with my purge solenoid somewhere. Turns out when I replaced my alternator I forgot to plug it back in so I assumed this was the cause of the SES light. However I never had the code cleared even tho the ses light did not come again for a week.

Then the light came on again yesterday and I had the codes pulled. Now I am getting a p0420 and the same p0443.
My question is, if I never had the original 0443 code cleared could it just be stored or could there still be an issue.

Also, what would be the best way for me to determine whats causing the 0420 code, from reading other threads I have determined its either the cat or an O2 issue. I just want to determine which one. I really had no previous issues other than the car mysteriously cut off a few times about a week ago.

Thanks

0443 will set as a record frame and must be cleared.

For the 0420 code....use this guide to step through trial and error repairs. Not sure when or if you replacd your 02 sensor, but it'* an easy and fairly cheap thing to do and something that should be replaced more regularly than not.

My o2 sensor is actually the original, I just reached 105,000 miles. I was planning on changing it anyway. How is the denso sensor thats on rock auto. It'* pretty affordable, I just want an opinion of it.