2 cats into one cat. easy to do?

[HappyHooligan]

So my whole replacing the O2 sensor got me thinking. My truck is a California truck but no longer in CA. If I replace the two cats with a single (non-CA) unit, will that mess up the computer which thinks it's still a CA truck or does it not care? Anyone do this? Is it an issue or am I over thinking it.

 

[TheDurk]

You will likely get a P0420 code and CEL as the single cat won"t perform to the Cali standard your ECM wants.