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Old 02-09-2012, 08:04 AM
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Default 2005 Altima 2.5L P0420 Code

I have a 2005 Altima with over 140,000 miles I have replaced the crank shaft sensor once almost exactly a year ago. I now have the P0420 code and I am willing to just change the O2 sensors first but wonder should I just replace the precat since it is almost guaranteed to go bad from what I have read on many post. Also thinking to make sure it doesn't ever happen again go to a precatless manifold. I have found those for less then $100
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Old 02-09-2012, 03:36 PM
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bennyb53 bennyb53 is offline
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Check this out:

OBDII Code P0420 NISSAN - Catalyst System Efficiency Below Threshold Bank 1 | Engine-Codes.com

Last edited by NissanTech; 02-09-2012 at 09:00 PM. Reason: Change Link
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Old 02-10-2012, 04:32 AM
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Gotta love the internet......the pre-cat is NOT almost guaranteed to go bad. If that statement were true, can you imagine the number of 2.5's on the road built since 2002 that would need a replacement pre-cat? The statement simply isn't true.

Don't replace the pre-cat unless you have replaced the O2 sensors first (as you said you were). Replacing them now (you have over 100k on them), will let you know if the pre-cat needs replacing. If the code comes back after resetting it after O2 sensor replacement, then, by all means, replace the pre-cat, but I sure wouldn't replace it for the sake of replacing it unless you want to spend the extra time and money for piece of mind.

Have you noticed excessive oil consumption? How often do you change you oil? To me, oil is the life blood of the system, (just like blood is to the body) and much can be learned from watching the level and condition.
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2002 Altima (daughter - totaled 12/2011 with 210,000 miles)
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Old 03-19-2012, 02:37 PM
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I would sure have the precat checked, I got the P420 code and I can tell you it takes very little mileage for the cat to destroy your motor. I've seen it TOO many times. The Nissan 2.5 is KNOWN for this issue and my motor was destroyed in a couple hundred miles.
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Old 03-20-2012, 10:18 AM
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Just go ahead and get an aftermarket header (if legal where you are) just for peace of mind. The engine sucking in some of the precat is too big of a problem on the QR25.
2005 Nissan Altima 2.5s

Mods: Custom SRI, SRS header, Vogtland Springs, Drilled/Slotted Rotors + Ceramic pads, Blue LEDs, Racingline Front Endlinks, Skar VVX-12s, Audiopipe 1500w, Hifonics 6.5" Components, More Soon..
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2005, 25l, altima, code, p0420

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