Is that possible that both catalyst converters go bad at the same time?

Question

2000 Mitsubishi Eclipse 2.4L, is that possible that both catalyst converters go bad at the same time? I have the codes P0421 and P0431

Answer 1

Yes, using low octane fuel is the #1 cause and #2 is not doing the maintaince and #3 is driving the problem is the car had any.

 

start by replacing the oxygen sensor first and using 91 octane fuel from Shell