In Dec my 03 CRV got P0845 and P0420 code for the first time. Its the first time I seen an engine light on. I had 157K miles in it.

Took it to the dealership and they fix the P0845 and cost $170.

They clear the P0420 and it last week it came back. The dealership clear it again and after driving 50 miles, it came back on.

I am going to visual check my exhaust and unplug/plug the 02 censor tomorrow.

Next month I need to do my emission test.

1. Is there anything else I can do?
2. Has the cat converter reach its shelf life?
3. Dealership said cost 1K to fix. I dont mind the fix, but what if thats not the problem?

Your advice?

Thanks!