Help! I have a 1998 Honda Accord, V6, with 150,500 miles....great car! Check engine light came on today. Honda dealership is booked all this week, so I stopped by a nearby Tune-Up Clinic Shop to get a diagnostic analysis. According to the technician, the machine reported a P0420 Code, Cat. Effic. Below Threshold. The technician said that the computer is recommending that I replace my catalyic converter, costing around $500. Has anyone had this problem? If so, were you able to correct it WITHOUT replacing the catalyic converter? I was planning a 500-mile road trip (one way) in a few days and now am worried if I will have car problems. Please advise. Much thanks!

 

Well, that depends on a few things...
I'd say 500 for a new CC is a little expensive. It's not that hard to change one of those out and performance CC are like 350.00.

I wouldn't think that it's something you'd HAVE to do immediately, but I dunno.

 

I have a 5th gen and i had the exact same code come up with i had my CEL checked. So replaced with a stock oem cat and went ahead and upgraded to header and cat-back while i was at it. CEL is still on. Car still runs great, still gets 34+ miles to the gallon. I'm thinking that it may mean the 2nd o2 sensor which is plugged into the *** end of the cat needs to be replaced. If that is the problem, then i probably didnt need to replace the cat. and yeah mine has about 150,000 miles on it as well. rear o2 sensor cost around $170-$200 if you get it from honda

 

I'm pretty sure there is a way to test the 02 sensor. Don't know exactly how. (multimeter probably) If you don't have a repair manual, I would suggest getting one. You can save yourself some cash by doing your own maintenance and or repairs. That is, if you don't take it to a shop for everything anyway.

 

I've read before something about cat... and... it said something like...."catalyctic converter does not go bad, if there's something wrong with it, there's something else that is actually causing the problem"...
And one thing, I've read too was that the inner structure of a catalyctic converter can not and will not operate properly when radiator fluid has leaked or gotten inside the exhaust piping, and excessive oil leak could do that as well.
You must find the right problem before buying a new cat.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chestnut_55 &raquo;</TD></TR><TR><TD CLASS="quote">still gets 34+ miles to the gallon. </TD></TR></TABLE>

WOW! I can't even get that with my Civic.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRXb18Turbo &raquo;</TD></TR><TR><TD CLASS="quote">WOW! I can't even get that with my Civic.</TD></TR></TABLE>
Yeah im kinda surprised myself, ill never get rid of this car. the gas mileage is wayyy too good to let it go.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gianinline &raquo;</TD></TR><TR><TD CLASS="quote">I've read before something about cat... and... it said something like...."catalyctic converter does not go bad, if there's something wrong with it, there's something else that is actually causing the problem"...
And one thing, I've read too was that the inner structure of a catalyctic converter can not and will not operate properly when radiator fluid has leaked or gotten inside the exhaust piping, and excessive oil leak could do that as well.
You must find the right problem before buying a new cat.</TD></TR></TABLE>

wish i would have known this information before i replaced the cat. my car had run lean for a little while (or so i thought, turned out to be the front o2 sensor had gone out) and someone told me that somehow that could melt the ceramic on the inner wall of the cat and it could become "inefficient" signaling the CEL. I dunno, i replaced it but damn i wish i could figure it out. a replacement rear o2 sensor from honda costs damn near the price of the new cat itself. any way to check the rear sensor or how to tell if it is at the end of its life? car doesnt run bad but that glowing orange CEL just bothers me. and im not gonna pull the light out of the CEL dash because ill still know something is wrong.

 

on an OBDII car you have a O2 sensor in your cat...you need to replace it. and yea 500 may seem like alot, but cats themselves are expensive...if you get one from an OEM manufacturer, its even more

 

you HAVE to have a catalyctic converter on a catalyctic converter equipped vehicle, federal law.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chestnut_55 &raquo;</TD></TR><TR><TD CLASS="quote">Car still runs great, still gets 34+ miles to the gallon. </TD></TR></TABLE>

must be nice...i'm stuck with 12 mpg in the city and 18 on the highway...but that's what i get for running up to 36-37 advanced ignition timing i suppose...

 

cat's DO go bad. they get clogged and do not perform properly. if someone told you they don't go bad, well you were lied to. i've personally seen a few cats that have gone bad, yes sometimes its something else that causes the cat to go back (ie, bad fuel, running rich etc) but it also can be from having it get hit underneath the car, age, not being run at the right temps... a bad O2 sensor can make you think that your cat is done as well, the secondary O2 (behind the car) is the O2 that keeps track that the Cat is doing its job. if it goes squirly then it may set a SES for the car. try pulling the O2 out and spraying it with carb cleaner and see if that changes the SES code, if not then it is in fact the cat.

best of luck

and for which cat to buy, go to any parts store, find a universal that is the same pipe diameter as your exhuast and just buy a cheap one. i have universal's on both of my cars and i pass emisson's flawlessly. buying an OEM one is just asking to get raped.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gianinline &raquo;</TD></TR><TR><TD CLASS="quote">I've read before something about cat... and... it said something like...."catalyctic converter does not go bad, if there's something wrong with it, there's something else that is actually causing the problem"...</TD></TR></TABLE>

Meineke!! LOL

It IS true... even if it's not just a single part that's broken or worn, SOMETHING caused that Cat to fail.

$500 for a new cat is ridiculous. That's Honda's price (kinda low actually). And while most OEM Honda parts are the best replacements, you can do better! For a factory replacement, you should spend $90 to $150, but no more than $200. For a universal performance replacement such as Magnaflow or Cat Co. you are looking at roughly $150-$240. For a bolt-on direct fit performance replacement such as Random Tech's cats, you are looking at $260-$280. Either way, $500 for Honda's replacement is one of the very few parts scams they run.

Either way. DO check your O2 sensors, look for stored codes in your ECU, determine if you're running extremely rich or lean by smell or extraneous deposits from your exhaust. Bosch invented the O2 sensor, so run to your parts store and pick up the $60 and $80 ones from them.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by janaka &raquo;</TD></TR><TR><TD CLASS="quote">...sometimes its something else that causes the cat to go back (ie, bad fuel, running rich etc) but it also can be from having it get hit underneath the car, age, not being run at the right temps... a bad O2 sensor can make you think that your cat is done as well, the secondary O2 (behind the car) is the O2 that keeps track that the Cat is doing its job. if it goes squirly then it may set a CEL code for the car. try pulling the O2 out and spraying it with carb cleaner...</TD></TR></TABLE>

More good stuff. Just be careful when handling your sensors. DO NOT get any of that cleaner or grease on the top side (perforated area above the nut, outside of the exhaust). The cat samples fresh air from this and also uses it to regulate it's reference temperature so it can provide an accurate signal.