Catalyic Converter

My 99 Honda Civic Ex 2dr check engine light came on and the error code
message was for my Catalyic Converter which I was told I need to
replace. I was also told that I do not have to but I should replace my
O2 sensors also just to make sure all is well.
O2 sensors are expensive and if I do not have to replace it then I
would not. I was wondering if anyone can tell me whether or not it is
ok just to replace the Catalyic Converter without having to purchase
new O2 sensors, even though the Computer Diagonistic only indicated a
problem with my Catalyic Converter.
My next statement and question is I called and Independent Muffler shop
and basically asked how much it would cost to put on a new Converter,
the guy at the Muffler shop asked me if my car runs fine, I said yes.
He also asked if my sensor lights come on and off, I said no, I told
him that I had the code erased from my car after using a Converter
Cleaner to see it that would help but no sooner the check engine light
came back on.
He also told me that it is not really necessary to have my Converter
changed because more than likely the check engine light will end up
coming back on.
He said some of the Manufacurers like Ford are trying to work on there
error codes with regards to Converters because it comes on too much and
that they are espensive parts to replace.
If there is anyone that have any info with regards to this please let
me know
Thanks

 

Mileage?

The exact error code? (It would be something like "P0420".)

 

It is not necessary to replace the O2 sensor unless a code comes up. The
computer keeps close checks on them just as it does on the converter. The O2
sensors can also be checked on an OBDII tester with diagnostic ability, not
the basic code readers. Mileage makes a difference as the converter should
be covered for 80k miles. Check your warranty information. If over 100k then
the converter probably needs changed.

 

I just went through the same exercise with my 99 Civic LX. This is a
chronic problem that can be blamed on a design defect of the exhaust
manifold. If you remove the heat shield located where your top O2
sensor resides, you will likely notice a hairline crack in the area
where the O2 sensor connects to the exhaust manifold. (you may have to
brush off some rust from the cast iron part to see it)

This crack is what is giving you a "check engine P0420 code"

Your O2 sensors are likely in good condition but you will have to pay
extra special attention when removing them from your old (Exhaust
manifold/Catalytic converter). They may be seized and you don't want
to damage them. If you purchase the Exhaust manifold/Catalytic
converter directly from Honda it will run you about $600-$800 without
the O2 sensors.

I purchase an aftermarket Cat from www.stevensparts.com for $170 USD +
Shipping. It's stainless steel and comes in two parts instead of the
original unibody. It resolved the P0420 Check Engine code. I have since
taken the car in for emissions testing (in Ontario, Canada) which it
passed with excellent results.

 

Curly the error code is P0420

 

Yes my error code message read P0420
Thanks

 

Did you see Busiu's post? That's the first mention I've heard of a cracked
manifold causing this error. If it's common, there ought to be a TSB sooner
or later outlining this.

My experience with the P0420 error is that it's mostly city-driven cars
that experience it, so it appears to be related to a cat that's
contaminated from lots of low-speed driving. Based on that observation, I
wrote this:
http://www.tegger.com/hondafaq/p0420.html

By the way, if you're in the US, there is an eight-year Federal emissions
warranty covering the cat. If you're in the US, a new OEM cat will come to
you at no charge. You may want to explore that first with your dealer.

I'm going to add Busiu's experience to the FAQ. If Busiu has any other info
to report, such as a TSB, I'd love to hear from him.

 

I'm unaware if an official TSB exists but my Honda mechanic tells me he
sees this problem all the time. It's also the primary reason why you
can't find an Exhaust Manifold for this generation of Civic at your
local wreckers. The good ones have been pillaged and the remainder are
cracked.