P0420 Catalyst System Efficiency Below Threshold | 4.6L Based Powertrains

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#1630014 - 12/03/08 07:25 PM P0420 Catalyst System Efficiency Below Threshold
Timmn1 Over the Hill Registered: 09/21/07 Posts: 1919 Loc: Near I-80 & I-57	So, about 1200 miles after the installation of the Shark plenum, I get a CEL. I don't suppose I can blame that on the plenum. I used my scanner to reset the light, but when it comes back, what should I try first, O2 sensors, cat, or both? _________________________ 1997 Grand Marquis GS - Died Now have a 2003 Grand Marquis LS
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#1630076 - 12/03/08 08:39 PM Re: P0420 Catalyst System Efficiency Below Threshold [Re: Timmn1]
TechnoWeenie Banned Posting Addict Registered: 10/02/04 Posts: 22857 Loc: The perimeter	Time to replace o2 sensors and cats _________________________
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#1630086 - 12/03/08 08:47 PM Re: P0420 Catalyst System Efficiency Below Threshold [Re: TechnoWeenie]
Colt45 less is more� Poobah Registered: 08/30/04 Posts: 6447 Loc: Moses Lake, WA	Try O2s first, they are the cheapest and may be it if they have many miles on them. _________________________ -Colton 2002 Ford Crown Vic PI, 201k "Highwayman" (Ex-Kootenai County, ID Unit #42) - Down for bad engine 2003 Ford Crown Vic PI, 103k "Th-wacker"
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#1630798 - 12/04/08 08:42 PM Re: P0420 Catalyst System Efficiency Below Threshold [Re: Colt45]
cfrank Member Registered: 10/28/08 Posts: 410 Loc: North Florida	Originally Posted By: Colt45 Try O2s first, they are the cheapest and may be it if they have many miles on them. X2, the o2 sensors are cheaper and with higher mileage they do go bad or at least get "slow". repalce the sensors, clear the code and go from there. But in my experience it is usually the cat. converters Edited by cfrank (12/04/08 08:43 PM) _________________________ 2000 Ford Crown Victoria P71 - Ex jacksonville,Fl PD unit# 160 Check out my ebay items!
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#1632629 - 12/07/08 02:53 PM Re: P0420 Catalyst System Efficiency Below Threshold [Re: cfrank]
Steve83 Poobah Registered: 10/03/04 Posts: 7454 Loc: Memphis, TN 38060, USA, Earth,...	Blindly throwing part$ at a CEL is the least effective and most expensive thing you can do. If the cat is bad, then the HO2S is GOOD because it's accurately reporting the problem. If the HO2S is bad (reporting a nonexistent fault), then cat is GOOD. Find out what's actually WRONG before buying ANYTHING. _________________________ Walk softly & carry a BIG SIX ! ! ! . . .
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#1667434 - 01/19/09 11:25 AM Re: P0420 Catalyst System Efficiency Below Threshold [Re: Steve83]
craftsmanracer Over the Hill Registered: 09/20/08 Posts: 2174 Loc: Englewood,Florida	I just got this code today, I had glasspacks installed about 3 hours ago, and I installed the shark plenum about a month ago. Help! _________________________ 1998 White Crown Victoria Police interceptor. setina pb-400 push bar, 75mm throttle body, 45$ granatelli plenum,1/2 intake spacer, home-made cold air intake, 20%tint, cherrybomb glasspacks Oh come on man. You got no lady fingers, fuzz buttles, snicker bombs, church burners, finger blasters, gut busters, zippity do das, or crap flappers? No, I don't. You're gonna stand there, owning a fireworks stand, and tell me you don't have no whistling bungholes, no spleen spliters, whisker biscuits, honkey lighters, hoosker doos, hoosker donts, cherry bombs, nipsy daisers, with or without the scooter stick, or one single whistling kitty chaser?
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