2001 Toyota Corolla rebuilt engine

Yes, it would not pass CA emmissions. Is it burning oil constantly or just on startup?
If just startup, it would be valve seals, if constant, then bad rings.

Thank you very much!

One month ago, I dive it for about 2 hours in the high way. The oil light was flashing. And the day when I left, I checked the oil and it was full at that time.

Last Sunday, the check engine light on and the code is P0420. I am not in CA. I don't know if it is OK for me to replace the cat converter with a universal one because the cat converter for CA is so expensive.

Check oil pressure with a mechanical gauge, that would be a big problem if oil pressure is low.

I have seen varying results with the universal CAT's. It is best to use an OEM replacement, but it is your money.

Thank you very much! I appreciate it very much!

I still have two questions:

If it is OK for me to replace an federal emission Cat converter to my car?

The price of OEM is around $1100. It is so expensive. Somebody told me if I don't need to repair it, there is some noise and it does not effect the car's running. Is it right?

Yes you can replace the CAT.

But before you do, perform a backpressure test. Remove the upstream O2 sensor and screw a pressure gauge into the O2 sensor socket, if pressure is excessive, then replace the CAT, if not then the CAT is OK.

A trusted shop can do this for you.

CAT's are generally ruined by lean/rich fuel mixture, or by an impact.

If the CAT is bolted on (most Toyota's are), then you can remove and inspect it, should look like a honeycomb, if any part is melted or broke, then replace the CAT.