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P0430 - Needs a Catalytic Converter??

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Re: P0430 - Needs a Catalytic Converter??

Postby thacounty [OP] » May 18 2017, 8:22pm

JoshInWV wrote:No there's some truth to that. I'd keep the old cats and fix the problem before subjecting new cats to an old 'cat-killer' problem.


When I say burning oil, I mean typical AFM oil consumption.
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Re: P0430 - Needs a Catalytic Converter??

Postby thacounty [OP] » May 18 2017, 8:23pm

Alex_M wrote:
thacounty wrote:Thanks everyone. It absolutely burns oil so it looks like I'll be stuck with bad cats every once in a while. I will probably go the cheap route since I can't stop it, short of a rebuild. Also, it does run a little rich, but I thought they all did. Will I lose performance with high flow cats? Won't higher flow move my torque and the HP curve out to higher RPMs

Thank you both!


No. Its such a small change in overall exhaust restriction that you won't notice any difference.

How rich is a little rich? They all are tuned to run slightly rich because rich is better than lean (for the engine)and the cats can handle it to a point.


Just a little rich like the other NNBS. It's only noticeable at WOT.
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Re: P0430 - Needs a Catalytic Converter??

Postby thacounty [OP] » May 18 2017, 8:24pm

grim jeeper wrote:It may be a long shot but have you check with a dealer I know GM extended the warranty on some cats...Asking is free


Thanks. I will give them a call.

Does anyone have a suggestion what Cat to use? I would like to get close to OEM, but not $900
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Re: P0430 - Needs a Catalytic Converter??

Postby Riley76 » May 19 2017, 5:48pm

I had to put new cats on my '08 back at 100k. The dealer wanted $1600+, so I went to my local mechanic and he did them for $700. Walker makes a nice direct replacement all in one unit just like whats on your truck now. They are like $500 or less. All bolt on, which in retrospect I wished I had just ordered them myself and saved on the labor. Just hit your flange bolts with some good penetrating oil, as they can break sometimes, like manifold bolts. And you will need a special O2 socket to get your O2 sensors out unless you can manage an open ended wrench, but they are in tight spots. Best of luck. The only thing I found once I had mine done is that the higher flow aftermarket cats would cause my emissions light to come on sometimes, because the sensors don't like the higher flow even though running live data logs showed my cats working perfectly like they should. Once I had a custom tune done by Lew here, I don't get that light anymore as he wrote it into the tune.
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Re: P0430 - Needs a Catalytic Converter??

Postby Hoagie90Hoagie90 is online! » May 19 2017, 10:01pm

idrivea2005sierra wrote:
Alex_M wrote:A shop can weld in universal replacements for MUCH cheaper than that unless you have to adhere to California emissions. If you take that route though, be sure to replace both. An aftermarket cat will have different flow properties and you want to make sure you have equal back pressure on both banks.

A lot can cause them to go bad. Does your truck burn oil like most NNBS trucks? There ya go. Running rich will also damage them and a few other things.


California is only difficult because of the CARB number supposedly stamped on the cat, meaning it will only fail visual not performance. I went through this nonsense with my VW. Dealership wanted 1300$ for the cat not including labor. I spent some time on the phone and long story short all cats are 50 state cats but CA requires a stamp. They all function the same and produce the same numbers in a sniff test. I ended up finding a bolt in replacement for 150$, had it shipped to my brother in AZ and he shipped it to me in CA. Passed with flying colors.

Vehicles newer than 2000 are now OBD2 scan only. They just check the computer for codes and values. IF the OBD2 port tells the emissions computer the car is running correctly the car passes. This is the exploit VW was using for the diesels. It went into a mode where the OBD2 output was "within range" and told the computer as such.



This is good to know. I am currently in the process of registering my Texas truck in California. I don't have CA legal converters, but I know she will pass emissions at least.
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Re: P0430 - Needs a Catalytic Converter??

Postby thacounty [OP] » May 22 2017, 3:04am

Riley76 wrote:I had to put new cats on my '08 back at 100k. The dealer wanted $1600+, so I went to my local mechanic and he did them for $700. Walker makes a nice direct replacement all in one unit just like whats on your truck now. They are like $500 or less. All bolt on, which in retrospect I wished I had just ordered them myself and saved on the labor. Just hit your flange bolts with some good penetrating oil, as they can break sometimes, like manifold bolts. And you will need a special O2 socket to get your O2 sensors out unless you can manage an open ended wrench, but they are in tight spots. Best of luck. The only thing I found once I had mine done is that the higher flow aftermarket cats would cause my emissions light to come on sometimes, because the sensors don't like the higher flow even though running live data logs showed my cats working perfectly like they should. Once I had a custom tune done by Lew here, I don't get that light anymore as he wrote it into the tune.


This is great info! Thanks! I'll look up the Walker kit. I have an intune. I wonder if I can tune them myself.

Luckily I have an 02 wrench, and that is great advice. I can't imagine getting these off without it!

If you happen to have a link, I'd be very interested.
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Re: P0430 - Needs a Catalytic Converter??

Postby GMT604 » May 22 2017, 4:22am

If you don't have to smog it and you just want the light out, just put spacers on the rear O2 sensors. No more codes. It won't affect the way it runs unless the cats plug up.
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Re: P0430 - Needs a Catalytic Converter??

Postby thacounty [OP] » May 22 2017, 4:26am

Thanks GMT

So I was driving it and the low oil pressure warning came on. I stopped turned it off, and restarted it and it was fine for a minute or 2 until it happened again. Limped home like this, not sure what to do. I'm guessing these 2 are unrelated? I just had the screen and oil sending unit replaced a month ago or so.
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Re: P0430 - Needs a Catalytic Converter??

Postby GMT604 » May 22 2017, 4:28am

Not related to the P0430 at all. Pull the sending unit and clean the screen.
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Re: P0430 - Needs a Catalytic Converter??

Postby thacounty [OP] » May 22 2017, 4:38am

GMT604 wrote:Not related to the P0430 at all. Pull the sending unit and clean the screen.


Thanks again! Any way to keep it from getting clogged up again? I don't want to have to clean the screen once a month if I don't have to.
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