catalytic converter question (2 Viewers)

[efjayatee]

I bought the rear and front Walker universal cats for my 96 because it has an interminent P0420 code. Has anyone welded just one of the 2 cats and did that cause any check engine light afterward? To clarify, the catalytics are not high flow (single cats)...thx MUD!

 

[CivicFerio]

You need to check the primary and secondary O2 sensor switching pattern. This is typically done with a scanner that is capable of oscilloscope function. I'm my case I have a lazy secondary O2 then I replaced it and I was able to verify my catalytic is bad.