Service engine soon light came on today, so I went up to Autzone just now and had them scan it for me and P0420 came up for the code. I looked on here what it means which is said, P0420 Catalyst System Efficiency Below Threshold. What would the problem be to look at?

Guy at Autzone told me it was one of these: Engine misfire or running condition, Large vacuum leak, engine oil leakage into exhaust valve guide, piston rings, cat converter defective (possibly do to previous causes), oxygen sesnors monitor the cat converters ability to store oxygen.

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R.I.P 2001 Se :(

That code means that the O2 sensor behind the cat is getting a low reading from the cat. I would check and see if you can shake the cat (while cold), and see if it rattles. If it does, then it is bad. Don't you have a magnaflow cat? That's probably your problem. They have less catalyst than the stocker, and the computer doesn't like that.

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Bye Bye:

RIP sandrock

Yea I have a magnaflow cat, brand new too it was put on about 3 months ago.

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R.I.P 2001 Se :(

Is this still the same problem from this topic you already made......?
viewtopic.php?f=8&t=12335&p=131207&hilit=P0420#p131207

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No those codes got fixed by cleaning the EGR valve and replacing the cat with a new one which is the magnaflow. Got the new one put on in July and the service engine soon light went away with the codes. Yeaterday at 5:30 am the SES came on and I got it scanned and that's what it said.

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R.I.P 2001 Se :(