I just replaced Cat Converter then I got OBD code P0420. Are they related? on 2003 Chevrolet S10

I had a P0300 code. Changed out fuel filter, throttle position sensor, cat converter, and coil for cylinder 2&3. The i got the P0420 code. If I just changed the cat with a brand new one, how can it be inefficient? Thanks for the Help.

by in Dunn, NC on October 27, 2011
2 answers 3 comments
ANSWER by on October 27, 2011
did you use a dealer cat or aftermarket?? the aftermarkets are cheaper but dont have enough precious metals to keep the light out. the dealer is more money but well worth it. Roy
COMMENT by on October 27, 2011
OK, That is good information. I appreciate your help. I used a Walker Converter from Autozone. I can reset the light and hope it stays off. If the light will not stay off, could it be that the part is defective?
COMMENT by on October 27, 2011
not defective, just will not work. you need a factory converter. just hope autozone takes it back. we never use walkers for this reason. Roy
ANSWER by on October 27, 2011
Make sure you have the P0300 issue fixed, what ever caused the misfire most likely caused the cat. converter to fail. The O2 sensor before and after the cat measure it's efficiency a bad sensor could inaccurately flag a cat code (P0420). Professional grade scan tool live data helps figure out troublesome codes but only as good as the person interrogating the data.
COMMENT by on October 28, 2011
I have an Actron CP9580 Autoscanner. I can get live data read out. I haven't been using it but just a few days. I'll have to do some research on all its functions. Thanks for the Help.

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