P0420 Code

Hi everyone,

I need some advice. Coming home my CEL came on and I just found its the P0420 code.

The code reader reads this: Catalyst System Efficiency Below Threshold (Bank 1)

Now this is the second time this code has come up, the first was a few months ago but after disconnecting the battery (I was wiring a light bar), the light went away.

This is a 96 sr5 with the v6 and it has close to 400k miles.

I don't think the 02 sensors have ever been replaced and I know they are a wear item.

I am thinking that one of them is bad instead of a bad cat but I wanted to run it by you all to get your 2 cents.

Oh and about the time the code came up the first time I noticed my milage dropped from 17 to about 14 city.

Thanks in advance!