2008 Lancer Engine code P0420
 

Hello all. I have 2008 Lancer ES and I've been getting this code: P0420 Code: Catalyst System Efficiency Below Threshold (Bank 1)
I have searched some and everyone pointing that it's Cat Converter. However, I tested voltage on sensors and it's how it's supposed to be according to internet. First sensor is going up and down and second is steady at 0.800. Does this mean that Converter is good?
I have to tested temperature yet because I just ordered laser temp tester and waiting for it to arrive.
If Converter is good, what else can cause it? I don't feel power loss or any other symptoms either. Does not smell or smoke.
Any ideas would be helpful.
Thanks

That is the worst car instructional video I have ever seen :D