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Re: 97 Mazda Protege P0421 O2 Placement
Posted to Emissions Forum on 1/19/2006

Hi Kansas,

It does seem that if they are going to have 2 cats inline that there should be a 3rd O2 after the 2nd cat. What this does is it leaves the door open to ignore the rear cat when doing an emissions repair.

I understand all that stuff about the fro... Login to read more.