P0420 Catalyst System Efficiency Below Threshold (Bank 1)
12-05-2005, 11:06 AM
#1
P0420 Catalyst System Efficiency Below Threshold (Bank 1) I took my car to autozone to get my SES scanned. This is the code they showed up. He said it was probably an o2 sensor but wasn't sure. Do I need new o2 sensors? Is this code hurting my performance? I have to get it fixed anyway since my inspection is due this month...
12-05-2005, 11:41 AM
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Originally Posted by SPL
I took my car to autozone to get my SES scanned. This is the code they showed up. He said it was probably an o2 sensor but wasn't sure. Do I need new o2 sensors? Is this code hurting my performance? I have to get it fixed anyway since my inspection is due this month...
12-05-2005, 11:54 AM
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I am assuming you are stock If not that could be your problem. However with 54000 on a 2001 i would be willing to bet that it is a rear O2 try swaping them and see if it goes to the other bank. If it still is on the same bank then your cat is dead and on something emmisions related like that i think they would have to replace it for free its not an extended warenty thing.
12-05-2005, 12:06 PM
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i doubt its an o2, if it was, it would probably show a bad o2 sensor, not a bad cat code, they tried that crap with me, they just dont like replacing crap under warranty. after the cat was replaced, no more light
12-05-2005, 12:13 PM
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Most likely a bad driver's side cat - they're covered under the federal emissions warranty for 8yrs/80K. There's pages of threads in the PCM Diag & Tuning forum, search there for "P0420" I know 2 people that had theirs replaced free.
12-05-2005, 10:22 PM
#7
Just get it cleared and see if it comes back. I had that code come up one day as I was lugging my car around (I had an older guy as a passenger and was tying to keep it quiet). I had it cleared, used some fuel injector cleaner in my next tank of gas, and it hasn't returned - been about four months.
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12-06-2005, 10:07 AM
#9
cars come from the factory with 8 year / 80,000 mile emission system warranty. its a federally mandated deal that all manufacturers that sell cars in America have to honor. its totally seperate from the bumper to bumper and/or powertrain warranties. if you switch rear O2s from side to side and the code stays on the driver side, GM gets to give you a new catalytic converter. and this problem won't affect engine performance.
12-06-2005, 03:56 PM
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Originally Posted by SPL
I'm taking it in the morning to the dealership to have the cat replaced. Could they deny the warranty if I have a lid?
my first went out at 51k..second at 56k..both replaced for free because of the warranty.
12-07-2005, 12:42 AM
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i had the same code on my 00 trans am. It was the cat, however since i have headers(even though they are shorty) it voided the warrenty they said, so i just bought a stock cat off someone for $30 and the car works fine now.
12-19-2005, 09:27 PM
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ok... my cel came on with the same code. I have 64k on the car, I don't have a cat off the end of the Y pipe... but are those cats that are built onto the stock exhaust manifolds that look like little boxs? my cars gas mileage has gone down pretty steadily the past few weeks before this SES came on.... I just filled up at 12.8 today... thats WAY off my 16 I used to get... and 14 is the worst previous with serious racing, none on this tank. I have had the car for 20k miles with no cat at the y pipe... 01 btw... and it has never thrown a cel.. I figured it was my o2's due to the poor gas mileage but you guys don't seem to think so?
12-20-2005, 11:50 AM
#17
i wouldnt think it weird to have either the 02 or the cat go out. At 60K our car was throwing CELs for a malf. cat too. This is when the car was as stock as yours. I would start there and if that doesnt work, i would go immediatly to the 02s.
