"Catalyst efficiency" code -- questions

From: Grady Ogburn (jgo@nospamplease.uswest.net)
Date: Sat Feb 28 2004 - 14:08:50 EST


Folks-

My Dak threw a MIL light. I used OBD-2 on my laptop to pull the
code: "P0420 - Catalyst efficiency below required level".

I've put just under 40k easy miles on the truck. Aside from the
sensor, which is original, the entire exhaust is aftermarket
with about 25k on it. The CAT is a 3" high flow unit.

I have no other reason to believe that the cat really is bad,
although I have developed a new "clunk" directly under the cab
that I hear when I'm cornering on bumpy roads, that I think is
unrelated. Bad CATs sound like a can full of marbles/gravel,
right?

I have a coupla quick questions.

1. Is it presumptuous to suspect the sensor rather than the CAT?
2. Is that code conclusive evidence that the rear O2 sensor is
out-of-whack?
3. Can the O2 sensor be cleaned, or must it be replaced? TonyC
(FAQ) believes you can use carb cleaner -- does anyone disagree?
4. Any special tools to swap an O2 sensor?
5. Does Bosch make the the best replacement part?

Thanks,
Grady

-- 
Grady Ogburn (Denver, AIM: JGradyO)
Black '98 Sport CC 4x4 5.2l, 5 Speed, 3.55 LSD
K&N GenII, MP TB, JET II, MSD 6A, Magnecor 8.5 Wires
Mesa Headers & Cat, Gibson/MagnaFlow 3" Exhaust 
Leer Topper



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