2006 4Runner V8 p0420 & p0430 codes

I just bought my 4runner a couple weeks ago and just had to fix the timing because the mechanic who replaced the timing belt for the dealer I bought from didnt do it correctly. It has been running good for the last week and today two new codes came up the p0420 and p0430 codes. I have been trying to find what the most common cause is before I go and start spending money in places that arent needed. Any help would be appreciated.

 

Could just be your downstream O2 sensors. If you change those and the code returns then it could be the cats. I didn't have p0430 just p0420 and changing my downstream O2 sensor on the driver's side got rid of it.

 

Well a parts changer would change the O2's and pray.

I'd personally take a meter to the 02s and see what you get first. See if you can get the voltage switching on it. OBDII Scanner should have it built in just get a half decent one.

 

It actually went off earlier today after driving it awhile so not sure what’s up with that