How to get rid of a P0421 CEL...?

[ghettoracingkid]

I forgot where the post is but someone said you can test the downstream O2.

I guess ill ave to suck it up since I changed the O2's not to long ago

 

[clos561]

isnt that too lean at idle cel?

 

[ericrapp]

how do you test the 2nd O2 sensor.

I think im having problem with my cat but I dont want to drop that kidna change if its not.

Take your car to a local auto parts store and have them read your codes, usually for free. really easy. then you could ask mazda or us whether you need to spend money on the sensor. Occassionally i hear the rear o2 will dirty up with rich conditions and not read well. And Mazda can run a resistance check on it. You will code if it fails, the ecu will detect it. I hope you can check out the codes to see what is up with exhaust. Mods can effect your ecu too as you probably know, but check em out for sure and good luck!