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Posted (edited)

I have a 2009 Silverado with the 5.3 engine 155,000 miles. Replaced the engine with an reman from the parts store a couple months ago. Was flawless until recently I am starting to get a P0430 code. I can clear it and sometimes it stays away for a few days and sometimes its the next day coming back. I have a bluetooth ODB2 scanner so I can also see if there are any preliminary P0430 before the hard set. Usually are when it is acting up. I tried swapping the trailing O2 sensors from side to side to see if the problem followed over to the other bank but no dice it stayed. While I had the O2 sensors out I slid my snake cam in the hole and the honey come material looks perfect. At least from the back side. No melting points or burn holes. I have a screen shot of my diagnostic software and it shows bank 2 sensor 2 ranging from .055v to .860v where as bank 1 sensor 2 holds steady aroun .740v. Just trying to grasp what else besides a bad cat that this could be. Engine was replaced due to AFM carboning up the piston rings and causing high oil consumption. This was turned off when I bought the truck but obviously not soon enough.
O2 Sensor reading.PNG
So I did some more tests tonight. On the bank 2 passenger side, the temp going in the cat at the #1 O2 sensor bung is 290 and after the cat the #2 O2 sensor bung is 460. So it looks like the cat is functioning as it should. I did get a scope on it tonight showing the two secondary O2 sensors and this was done starting out at idle then going to about 1500-2000 rpms. You can see the dip on the green line which is bank 2 when I accelerated off of idle. Then holding it steady it had momentary blips down where as bank 1 stayed steady. Any help with this issue would be greatly appreciated.

o2 sensor scope.png

Edited by Budro12345

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Needs a cat!

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Even though the honeycomb material looks good from the #2 o2 sensor and it shows it increasing in heat from inlet to outlet like it should?

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Looking good and being good can be two different things. It may look great and even your using your temp gun may show great results like it's working okay but it could still be something where the inside of the cat has got to the point where it no longer functions good enough for what the sensor wants.

 

If the bank 2 sensor is switching more than bank 1, that is a sign of an issue for sure.

 

I don't think it means you have to replace it, because it's not plugged up or hurting performance at all. I'd try doing the spacer trick with the o2 sensor. You take a 2 spark plug non foulers, drill one out, install the o2 sensor and thread it back into the bung on the exhaust. What you are doing it spacing the sensor out of the exhaust stream more and it can help keep the code away.

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5 hours ago, Budro12345 said:

Even though the honeycomb material looks good from the #2 o2 sensor and it shows it increasing in heat from inlet to outlet like it should?

If a sensor was bad, there are codes for them.  You have a bad cat code.  Get a good one and not a Chicom special or you'll be doing it again in a year or so.  Your mileage is suffering too a little right?

 

Some folks have "restored" them by driving at highway speeds in a low gear to get them real hot and burn off whatever contaminants fouled them in the first place.  Didn't work for me, I put on new Magnaflow cats and y-pipe.

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For 25$ you could try cataclean,you mentioned, previous high oil consumption,that's the contaminants in the cat,and bank 1 is a little high also,.6 is more of a # I see

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@riverbanks I tried the cataclean and some high octane gas. Looks like that may have taken care of the issue as my graphs are alot flatter now for the downstream O2 Sensors. Same engine RPMS as what the earlier scope showed. Not perfect but getting better.

o2 sensor graph 2.PNG

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Well the light came back on. Code came back. I live about 15 mins away from work. So it never comes on going to or from work after sitting cold. If I go somewhere, let it sit for maybe an hour and then drive around it will pop the code. Like the cat hasn't cooled off or heck I don't know. Just weird, I can go a whole week of just driving back and forth to work and no codes. This is primarily highway driving though.

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14 hours ago, Budro12345 said:

Well the light came back on. Code came back. I live about 15 mins away from work. So it never comes on going to or from work after sitting cold. If I go somewhere, let it sit for maybe an hour and then drive around it will pop the code. Like the cat hasn't cooled off or heck I don't know. Just weird, I can go a whole week of just driving back and forth to work and no codes. This is primarily highway driving though.

Mine were that way then would throw a code at shorter and shorter intervals.

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2 hours ago, swathdiver said:

Mine were that way then would throw a code at shorter and shorter intervals.

Did you have to end up replacing the cats @swathdiver?

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10 hours ago, Budro12345 said:

Did you have to end up replacing the cats @swathdiver?

Yes!  One cat had been replaced prior to purchase and this one failed first and the other factory one about a month before we replaced the entire Y-Pipe.  I bought the Magnaflow system with 2 new cats and the resonator/cat.  Sold the old y-pipe and "3" cats to the scrap yard for some money.  The design and flow of the pipes has improved performance, picked up about 7 horsepower at the rear wheels compared with 2-3 months before replacement.

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