Bad cat?

[DallasTahoe]

They shouldn't bounce, more like a wave if charted. Replug connectors, Ohm check Sensors, Check wires for wear thru or Pinch spots. Might just be bad O2's. Heater circuit is troublesome, may need to wring out the harness. If cats were gone you likely would have performance issues/missfires.

I say bounce, they were going up and down, but bank 2 wasn’t moving the same as bank 1, And she’s drinking a lot of gas that’s for sure


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[exp500]

Being thirsty is the biggest indicator, You need a tune up. Once she loses 2 mpg consistantly it's time.
Minimum is new cap. You could monitor live data to determine how far you want to go on tune up. No history, do it all.

 

[east302]

Here is the GM diagnostic table for P0430. I thought it might help but it looks like it was written around a Tech2 (step 5).








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[DallasTahoe]

So finally had time to check it out, had it running and it was rattling, so I tapped on the cats and I could hear something jumping around inside, so definitely bad cats. Now I was going to go with Bosal cats, they got them on rock auto. But I found some through muffler express. They’re cheaper and they give free shipping, but I’ve seen a couple posts about bosal being better than most other brands, anyone know anything?


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[BG1988]

98 Yukon 4wd, keep getting code p0430, says catalyst system below efficiency threshold bank 2. Would that be the catalytic converter? I replaced all the o2 sensors a couple years ago just as basic maintenance. Thoughts?


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it's not the CAT you need to have P0420 and P0430 code (4 codes) I had both these codes on and off my self and was able to pass smog without issue.. turned out to be a faulty spark plug and baro for me... the ceramic blew it self apart (the spark plug tip)

if the temp is over 400-700C then they're working ok over that you might be misfiring aka fuel dump or your very high RPM...


check the spark plugs cold engine...


I would check out the MAF sensor this is a typical issue on the older ones i.e GMT800

 

[PatDTN]

I'll toss my experience in here. My cats collapsed completely blocking my exhaust. Right before that I got the same error.

 

[DallasTahoe]

it's not the CAT you need to have P0420 and P0430 code (4 codes) I had both these codes on and off my self and was able to pass smog without issue.. turned out to be a faulty spark plug and baro for me... the ceramic blew it self apart (the spark plug tip)

if the temp is over 400-700C then they're working ok over that you might be misfiring aka fuel dump or your very high RPM...


check the spark plugs cold engine...


I would check out the MAF sensor this is a typical issue on the older ones i.e GMT800

The cats are bad, I can hear stuff moving around on the inside when I tap on them


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[BG1988]

The cats are bad, I can hear stuff moving around on the inside when I tap on them


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what is the temperature?

if you really think it is the CAT

check out the
Aftermarket Catalytic Converter Database It will tell you which ones that work perfect for your SUV...


I suggest a "Walker" cat that is what i used on my old car . and it worked perfect as well had it for 4 years tell i sold it.. Don't let them steal your old cats though you can get a lot of money on ebay for them...