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02-21-2011, 11:36 PM | #1 |
Registered User
Join Date: Jan 2007
Location: pittsburg kansas
Posts: 894
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po420 and po430
96 yukon, 4x4, 5.7l.
Its throwing a po420 and po430code. the po420 pops up about every 60 miles or so. the po430 just came up for the first time today. I know its cat efficiency low. What are some possible causes? Good starting test procedures? Any common problems associated with these codes and trucks? Thanks in advance |
02-24-2011, 07:26 AM | #2 |
One day...
Join Date: Apr 2008
Location: Tuttle, Ok
Posts: 9,240
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Re: po420 and po430
Anyone have an idea or need more info?
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02-24-2011, 12:12 PM | #3 |
laying low
Join Date: Mar 2001
Location: Searcy, Ark. USA
Posts: 12,957
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Re: po420 and po430
Scott there is probably a list of PO codes already posted here somewhere. It might be helpful to make a sticky out of that. Just a suggestion.
I know the PO430 is "catylitic activity below threshold". It means the cat ain't doin as much as it should. It can be a cat just gone bad and it can be something upstream has caused it to go bad. Burning overly rich, burning oil and burning antifreeze can all cause a cat to go bad. The 02 sensor behind the cat monitors the cat's activity only. How well does the truck run upon cold startup and when warm? Strong smell of gas when cold? Down on power when warm? I don't remember what the PO420 code is for. Scott?
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Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross |
02-24-2011, 07:32 PM | #4 |
One day...
Join Date: Apr 2008
Location: Tuttle, Ok
Posts: 9,240
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Re: po420 and po430
Ya if you find it before me pm me and ill make it a sticky to put the the FAQ thread that is a sticky.
I dont remember much codes, its been a bit since i have played with code readers and kept up on all that. |
02-24-2011, 08:13 PM | #5 |
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Join Date: Jan 2003
Location: Denison, Texas
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Re: po420 and po430
How does it idle and how does it run at wider throttle openings?
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1998 GMC Sierra SLE 1/2 ton 2WD 305 Vortec -Gibson Stainless Cat Back Swept Side -SS Wheels 2005 Honda CRF250R 2006 Honda CRF150F |
02-24-2011, 08:17 PM | #6 |
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Location: Denison, Texas
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Re: po420 and po430
P0420-Three-Way Catalyst System Low Efficiency Bank 1
P0430-Three-Way Catalyst System Low Efficiency Bank 2
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1998 GMC Sierra SLE 1/2 ton 2WD 305 Vortec -Gibson Stainless Cat Back Swept Side -SS Wheels 2005 Honda CRF250R 2006 Honda CRF150F |
02-24-2011, 10:15 PM | #7 |
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Join Date: Jan 2007
Location: pittsburg kansas
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Re: po420 and po430
yes thats what the codes are, sorry i was a little tired when i first posted and just assumed everyone new what the codes where. Sorry it was my bad.
i have found out I have bad cats. Both rear o2s where crosscounting the same as the fronts, and they shouldnt, the job of the cats are to do away with any rich or what not mixtures and then the rear o2s should steady out and read a good mixture, well they were not. After we do not have emissions testing I took the cats out and welded in pipe. I sold them at the scrap yard for 40 a piece, then spent 8 dollars and built my own o2 eliminators. Very simple to do, and the codes do not come on anymore. Thanks for everyones help. |
05-16-2011, 11:31 PM | #8 |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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Re: po420 and po430
just be ready for insufficient EGR flow codes in the future.
the #1 reason I see P0420 and P0430 is coolant leaking past the intake gaskets. coolant contains silicates. silicates create a coating on the converter substrate blocking it from performing the necessary chemical reactions. it doesn't take a large leak. a very small leak, even vapors, over an extended time will do this.
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05-17-2011, 09:58 AM | #9 |
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Join Date: Jun 2001
Location: Benton, AR "The Heart of Arkansas"
Posts: 10,880
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Re: po420 and po430
GM had a cheesy catalyst media when they first started using Cats, but the media used now is pretty techno-savvy. Whereas the early ones were filled with a palladium-coated ceramic-type ball-shape, the later ones look like honeycomb and are fairly complex in their design. If you look at each end, you'd think that it is a straight-thru flow, but it isn't. The media isn't heavy, but stick it inside the shell and it gains weight.
Hope it all works out for you.
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Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was. |
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