OK Guys, help a brother out. My truck is a 2004 Sierra 1500, 4.8L V-8, has 72000 miles on it. I am going to put as much detail in this post as I can.

I changed the oil yesterday. I also inspected my air filter, found it to be in good shape, and replaced it. My wife got in the truck and drove it, and the Check Engine Light was on. Truck is running fine.

Definition of code from the Autozone check is:

Catalytic efficiency low-bank 2

Explanation: the oxygen sensors monitor the Catalytic Converters ability to store oxygen.
Probable Cause:
1. Catalytic converter defective, possibly due to one of the following:
2. Engine misfire or running condition
3. Large vacuum leak
4. Engine oil leakage into exhayst valve guide seals, piston rings

I feel sure that somehow I screwed up a sensor when I inspected the air filter. I have since re-seated the filter, re-seated the electrical connections to the sensor atop the air intake hose, and disconnected the battery for 20 minutes to see if the light would reset. The light is still burning.

You fellas got any idea what I need to do? I figure before I spend $70 and attempt to replace the oxygen sensor I would see what the auto board has to say.

Oh, and for what it's worth this is barney94. I did not realize my wife (Agism95) was logged in.





[This message has been edited by Agism95 (edited 5/21/2009 10:53a).]

I may be way off base here, as I am not a car guru. Mine pulled that code, as it was a bad catalytic converter. I called the dealer and it (the cat) had a 100000 mile warranty. Took it in, and they fixed it free of charge. Problem solved. The vehicle had 99800 miles on it. How lucky did I get? point being, if it is a bad cat, perhaps there is a warranty on it.

That's good info...hopefully it does not come to that!

Take it into the dealer Post haste for Cat converter replacement.

What is that going to run me?

$0.00 if it's under warranty, which is what you need to find out.

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Eh. The plugs arent always the same.

Thanks a lot, guys! I am under warranty and have a service appt. set up.

Now, another question, perhaps related to the fact that I disconnected the battery...perhaps unrelated, who knows, but it was fine before.
My A/C is not working and neither is my rear defroster. This leads me to believe that a fuse or relay controlling that control panel got blown or something.

I have checked every fuse that even looks related to that and none are blown. Any ideas? If not I'll get them to figure it out when I take the truck in, but that won't be cheap I'm sure.

Disconnect the pos terminal for 1 minute and reconnect it. But dont do it until you get the car back from the dealer. Doing so, erases the code and then they'll weasel out of changing the cat.

Thanks man. For what it's worth, I disconnected the NEGATIVE terminal before I checked your post. I did get the A/C back and I still have a check engine light, so hopefully I am ok. I can run by an Autozone tomorrow and make sure it pulls the same code if I need to.

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Why go through the trouble? Everyone knows P0430 and P0420 are 90% of the time sheety cats. Its a known issue on that gen Silverados.
Then if you do mess with them, that will be the only clean spot underneath, opening up the dealer to "well wtf have you been doing underneath?"

I say take it in and be done with it.

[This message has been edited by 1agswitchin4lanes (edited 5/21/2009 9:05p).]

So 1ag, since I still show a check engine light even though I disconnected the neg terminal, I should be ok (code not erased), right?

[This message has been edited by Agism95 (edited 5/21/2009 9:34p).]

Yeah, its obviously pending and you've thrown the conditions enough time with a KOER to throw a light.

Youll be fine.

Sweet, thanks for all the help. I really appreciate it.

mine threw that code alot after i replaced mine with Hi-flow cat mid pipes... i jst had to tune it out a little and its not a problem anymore.

obviously if you havent jacked with the cats and it s throwing it, then you shoul dprobably just get the factory cats replaced.