alright guys, my 05 5.3 is "knocking" but it will sometimes go away after the truck warms up a little. I went and scanned it because the check engine light came on but it had been doing it for about a week before it threw any codes, the code was p0420 catalyst efficiancy low threshold bank one...any ideas??

 

either one of your catalytic converters is shot, or just the O2. Most likely the cats,....time for longtubes and a Y pipe.

 

Keep in mind, your cats are warrantied for 8 years/80,000 miles by Federal mandate.

 

wow, im an idiot hahaaa, appreciate the advice guys, really. I think i may just pull the cats down and gut em, try and fool the T.S.I. people.

 

just buy an ory its a lot easier.

 

Converters rattle sometimes when the catylist is coming loose. Sometimes it's a knocking noise.

 

alright, so about two weeks ago that rattle from my cat quit. Yesterday i was just walkin around my truck and found the guts from the cat converter sittin in my exhaust tips...anyone ever heard of this before? I think its pretty cool that the cat gutted itself if only a little.

 

Does your truck have a tune or a cam in it? I have been told that the rich fuel mixture that is needed to run modifications can prematurely cause the cats to fail. Not sure if thats what happend in your case but its a possibility.

 

no cam, no tune...91 and up octane only though.

 

Man thats weird! I have never heard of a cat blowing out so soon on a stock engine! you might want to consider checking with the dealership. There might be something they know that we don't.