CEL Code PO420

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04-29-2005, 02:52 PM

Castle

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CEL Code PO420

P0420, "Catalyst System Efficiency Below Threshold (Bank 1)"

I'm a newb! first post! I already need help! I've been lurking around the boards for about 4 months now and have learned alot about my 2000 runner, I just got it about 5 months ago. here she is:

I'm receiving a CEL Code PO420 "Catalyst System Efficiency Below Threshold (Bank 1)"

I have just recently had the timing belt, p/s belt, a/c belt, serpentine belt, water pump all replaced, oh yeah rotors and brk pads too.

Within the same week I had the work done, the CEL Code started coming up. I reset it by removing the negative battery connection after having the code read by advance auto.

It stayed off for a few days, came back on, ran it again, once again same code, It's odd because it will stay off for about a day or a 2.5 hour trip.

I took it back to the garage and talked with some other folks and everyone seems to say Oxygen/o2 sensor, man those things are pricey too..

my question: Does the Oxygen sensor make sense to replace to fix this CEL code from coming on? (btw: the truck is running great and seems to be getting good flow from the exhuast)

I searched and came up with this https://www.yotatech.com/showthread....highlight=p0420

Last edited by Castle; 04-29-2005 at 02:53 PM.

04-29-2005, 02:55 PM

WATRD

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It's either a problem with the O2 sensor or the cat. My money is on the O2 sensor.

DTC No. DTC Detection Condition Trouble Area
P0420
After engine and catalyst are warmed up, and while vehicle is
driven within set vehicle and engine speed range, waveform of
heated oxygen sensor (bank 1 sensor 2) alternates flatteringly
between rich and lean (2 trip detection logic)
Gas leak on exhaust system
A/F sensor (bank 1 sensor 1)
Heated oxygen sensor (bank 1 sensor 2)
Three–way catalytic converter

04-29-2005, 04:51 PM

Robinhood150

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Castle, this thread belongs in maintenance and repair section, that's why I moved it the first time.

04-29-2005, 05:49 PM

Castle

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I knew I wasn't losing my mind, I thought I had posted it over there earlier and moved it, sorry about that.

thanks!

thanks for your help WATRD

thanks for anyone else's help also!

Last edited by Castle; 04-29-2005 at 05:50 PM.