p0420

hi guys i have 2009 prius it has code p0420
i cant see any leaks or anything cleaned maf .
i have attached freeze frame data . Any suggestion and diag method are highly welcomed.
thanks

Low temp at cat output and 02 sensor high/low indicates cat not working properly.

cj1 wrote: Low temp at cat output and 02 sensor high/low indicates cat not working properly.

+1

Fuel trims look good, no exhaust leaks found, sensors appear reactive... Sounds like a bad cat.

I'd suggest clearing the code and rechecking the catalyst monitor, if you haven't already. If you can reproduce the code, then it's probably cat time.

I have yet to encounter a false P0420.

I have fixed cat codes with new o2 sensors before. Not many, but a few. If you can look at mode6 data, if the cat is barely failing or it has old o2 sensors or if the o2 sensors are barely passing the monitor in mode6 data, then you can replace the o2s first. You are likely replacing them anyway when you replace the cat. Last one was a traverse, p0420, mode 6 showed the last cat monitor as passed, replaced the o2 sensors then the cat showed enough life to last a while longer. Doesnt always work, most times they just need a cat