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PO421:Warm Up Catalyst-below threshold (bank #1) CEL

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Old Jan 12, 2012, 10:03 PM
  #46  
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Originally Posted by Waldo1090
I have had this code for years, I've changed o2 sensers, and didn't fix it. I think I'm gonna get the magna flow high flow cat from RRM to see if it works, but with this code is it the first or second cat? If it's the second cat it should work right?
Yes its due to an issue in the ecu that causes the cat to fail. Its not an 02 sensor fault its telling you the 2nd cat is bad so to answer your question yes it will fix your problem.
Old Jan 21, 2012, 05:11 PM
  #47  
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a highflow cat is not going to fix your problem. the code is telling you that the catalytic converter that is built into your exhaust manifold is bad and overheating. the 2nd cat under the car isn't even monitored by the system. your o2 sensor goes in the front of the cat at the inlet. not on the outlet. i would recommend buying the rrm header and installing a cel eliminator to fix the problem. the aftermarket header will give you better flow and also remove that stupid cat. i have a rrm header, magnaflow highflow cat, and piggyback for sale since i went turbo. pm if interested
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