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HELP... Error Code P0421, "Warm Up Catalyst Below Threshhold"

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Old Oct 4, 2004 | 01:04 PM
  #1  
RacinMylancer's Avatar
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HELP... Error Code P0421, "Warm Up Catalyst Below Threshhold"

Can anyone help me?

Plugged an OBD II scanner in today and found out my CEL is on because of "P0421" "Warm Up Catalyst Below Threshhold"...

I don't have a service manual and I don't know what the warm up catalyst is. Feel free to call me an idiot, and tell me I know nothing about my car, but after doing so, please give me some advice. Is this something I can fix on my own? Can a "generic" shop take care of this for me? Do I need to go to Mitsubishi (please, please, don't tell me that...)?

Any help will be appreciated and probably reciprocated, if you live around me. Feel free to AIM me or give me a call or whatever. Cell's 714.716.6102. Name's Scott.

Thanks

Last edited by RacinMylancer; Oct 4, 2004 at 01:08 PM.
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Old Oct 4, 2004 | 01:10 PM
  #2  
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From: QC
Originally Posted by RacinMylancer
"P0421" "Warm Up Catalyst Below Threshhold"...
Did you change your header?
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Old Oct 4, 2004 | 01:19 PM
  #3  
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nope. only mods are breather mods... short ram intake and exhaust. stock headers intact. i don't think the aftermarket header guys were getting the same error code anyway...
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Old Oct 5, 2004 | 12:45 PM
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bump... help please?
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Old Oct 5, 2004 | 12:46 PM
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testpipe/cat delete? That error code is to tell you that its getting a funny reading at the 2nd O2 sensor.
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Old Oct 5, 2004 | 06:22 PM
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none of the above. 2nd cat is gone, but the 2nd o2 sensor is behind the first cat and before the 2nd, so that can't be the issue.

any other input?
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Old Oct 14, 2004 | 01:25 AM
  #7  
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did you ever find out what happened?
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Old Oct 14, 2004 | 10:09 AM
  #8  
03OZLancer's Avatar
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I got a test pipe and I don't a CEL. Are you sure the O2 sensor and ECU harness are all plugged together tightly? Could your first cat be cloged?
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Old Oct 21, 2004 | 05:25 PM
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Originally Posted by RacinMylancer
i don't think the aftermarket header guys were getting the same error code anyway...
Yes it is, that's the one I got after the header install.
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Old Oct 22, 2004 | 02:04 PM
  #10  
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k, got it figured out; exhaust manifold was bad (cracked, whatever... service manager didn't tell me, cuz his tech didn't tell him), but they're putting a new on one under warranty, so i'm not stressin'.
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