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check engine light codes


New Member
May 3, 2013
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Year, Model & Trim Level
1997 Ford Explorer
Hi all, new guy here! :exp:

I've got a '97 Explorer. I hooked the scan reader up today at work. The codes I got were: P0420 and P0430. I know they have to do with the cat, but I was reading to first check the O2 sensors, and if the light still remains then to change the cat? I've never replaced an O2 sensor before, but heard it wasn't too tricky. So my question is, how does one change the sensor, or does anyone have another suggestion as to what to look for?

Also, for both the codes, P0420 and P0430, the scan reader read "CNF" and "PND". I was wondering what these meant, as well.