1997 GMC Seirra P0420 and P0430 codes

Sierra · **Joined:** Sun Dec 21, 2008 4:02 pm **Posts:** 2

Code P0420 came up. I erased that code and after 100 miles P0430 came up. This goes back and forth after erasing codes. I have new cats ( Magnaflow ) and installed new o2 sensors last year. The sensors were not the most expensive type.
Could cheap sensors cause this problem? Or could it be something else?
I have a little over 126,000 miles on it and it has the 5.7 liter V8.

Sponsored Links · **Joined:** 29 Jun 2004 08:12 pm **Posts:** N/A

FergusonTO35 · **Joined:** Mon Sep 08, 2008 9:35 pm **Posts:** 154

Sounds like you need new catalysts to me.

Sierra · **Joined:** Sun Dec 21, 2008 4:02 pm **Posts:** 2

I have new cats. They are from MagnaFlow.
I tend to believe the oxygen sensors are the problem or maybe the computer.

Mohawkmtrs · **Posted:** Sun Dec 28, 2008 10:53 am

With cats, you get what you pay for.

I agree with Fergy.

Get your money back and get some quality cats.

asecmt · **Posted:** Sun Dec 28, 2008 5:20 pm

O2 sensors will not cause these codes. These converters are probably performance replacements where it does not matter where the light is on or not.

Skydrol · **Joined:** Wed Oct 08, 2008 11:32 am **Posts:** 165

Just as a side comment....

I am not big on those High Performance aftermarket stuff. IMHO is not a good return on investment. They do not give enough gain to get your money back.

Today's engines they put out a lot of power with just OEM parts without no much room to improve without sacrificing some (fuel economy or driveability or noise or pollution or a combination of all).

I remember my dad's 75 Monte Carlo with a 5.7 (350) V8 only made 145 HP, now any 4 Cylinder puts out that much. :lol:

1997 GMC Seirra P0420 and P0430 codes

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