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2002 chevy trailblazer_ltz
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96 Posts
Discussion Starter #1 (Edited)
Cat burned up

Recently kept getting a SES code P0420. SUV has only 53K miles on it. First tried tightening my exhaust manifold. Which had about 8 of the 12 bolts very loose. Drove the vehicle for about a week a SES trouble code P0420 came back. Next tried a new pre cat O2. Went about another week and code came back. Went to my buddy's muffler shop. Was told 99% of the time its a bad cat. Had him cut it off and found it melted inside and about 3/4 of plugged up. My buddy said i should have it checked out because it should have never done this. Went to two different mechanics I've used in the past. Both asked if I had a SES light on now. I told them no and I never got any other code than P0420. They told me if no light is on don't worry. Went to two different dealers and asked the same thing. Was told the same thing. If the SES light is not on don't worry. I asked what caused my cat to fail. Was told it was probably a bad cat. And the muffler shop is just trying to protect its self. Well our they BSing me or do I not have a problem and it was a bad cat. I have seen several people on here with bad cats and a P0420 and no other code. Did any of you have this happen. Replace the cat and then no other problems. Or was there a problem that was found later. Thanks for any help.
 

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2003 chevy trailblazer_lt_ext
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967 Posts
The only thing they are correct about is the bad cat is just a symptom. There is something wrong that caused it to fail.

However, they don't always throw a code. My cat plugged and I never got a code. That's the case with many failed Trailvoy cats. In my case, I didn't realize I was running cold. I can't be certain but I believe this is what caused my cat to fail. The temp gauge should be right on 210 or just the left of 210 but "kissing" the 210 mark. Any lower and it's running too cold. I have no idea how long mine was running like that, but I'm thinking it was more than 6 months. I put a new thermostat in and now its at the right temp.
 

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2002 chevy trailblazer_ltz
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96 Posts
Discussion Starter #3
Temp gauage is alwys at 210. and truck has run great since day one. I was wondering if my exhaust manifold was loose enough to cause this.
 

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2002 chevy trailblazer_ltz
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2,762 Posts
Temp gauage is alwys at 210. and truck has run great since day one. I was wondering if my exhaust manifold was loose enough to cause this.
Well that means your gauge is bad or censor.And then on top of that your stat could be bad and cause it to run rich and clog the cat.
 
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