Catalyst Above Threshold Limit (bank 2)

[alno1995]

2004 4.8L Sierra with 58K miles. checked it with code checker and says "catalyst above threshold limit (bank 2)", cleared it and it came back a day later. Always comes on when idling and engine warmed up. If it is an o2 sensor then which one?, or do I need a different code checker to find out? If it is converter is that covered under Federal warranty 8/80K? ( I am not original owner). Could new spark plugs help? probably has original set. Any advice from an experienced expert always appreciated. Thanks in advance

[Nytemare]

2004 4.8L Sierra with 58K miles. checked it with code checker and says "catalyst above threshold limit (bank 2)", cleared it and it came back a day later. Always comes on when idling and engine warmed up. If it is an o2 sensor then which one?, or do I need a different code checker to find out? If it is converter is that covered under Federal warranty 8/80K? ( I am not original owner). Could new spark plugs help? probably has original set. Any advice from an experienced expert always appreciated. Thanks in advance

If its an O2 it usually sets an O2 related code...chances are you have a buggered cat. And yeah it should be covered under the warranty.

 

Your plugs should be fine if your under 80K...100K is the change interval...but changing them early is never a bad idea....but it wont make your code go away.

 

There are some additives you can get that are supposed to clean your emissions system....I don't know how good they work though...but from the sound of things your running rich on the right (passenger) bank. If you don't clean your injectors every oil change or so, this could be the culprit. I would run a can of Seafoam through the engine and fuel tank with a full tank of fuel to see if it changes anything before I changed the cat...but if its free...you may as well get it changed out anyway.