CAT Problems
Thread Starter
Teching In
Joined: Aug 2004
Posts: 3
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CAT Problems Hi all. I was hoping some of you could help me figure out a problem and solution. I keep getting a recuring "Catylyst SYS efficiencency below threshold bank (2)" error code. I've replaced the O2 sesors before and after the CAT and still get the same code. I currently have brand new O2s on bank 1 and 2, before the CATS, and original equipment, after the CATS. I'm thinking that I need to replace the CAT on side 2, but can't figure how it went bad after only 29,000 miles. 
What do you guys think?
What do you guys think? 
TECH Senior Member
Joined: Dec 2001
Posts: 5,399
Likes: 3
From: Jacksonville, FL
Most likely it IS a bad passenger side cat (P0430). Friend of mine had his driver's side (P0420) replaced free at 20K by the dealer under the federal emissions 8yr/80K warranty. Don't know why it went bad but you can find more info if you search for the codes in the PCM diagnostics and tuning section.
GM is notorious for junk cats. My Camaro lost the drivers side at about 15,000 miles, and my Silverado just lost the drivers side at 55,000 miles. Bring it to the dealer, cats are warranteed for 80,000 miles. 
Joined: Nov 2001
Posts: 34,631
Likes: 2,555
From: Schiller Park, ILL Member: #317
Originally Posted by GM Muscle
GM is notorious for junk cats.
I've had over 10 GM cars that came stock with cats ranging in age from 1976 to 2004 and I can't ever recall one loosing a stock cat before at least 80K miles. Some had well over 100K on the stock cats. I've got a '76 Eldorado with the stock cat (They were HUGE back then) and 120K miles of use. I hope my luck holds out.
