I have a cat code P0420 in a 99 Civic VP with 120k miles. I understand there is a 8yr/80kmile mile warranty on this.

How likely is it to be the cat? I see things in other areas like ODB sensors, o2 sensor, clogged injection system, clogged egr port. (i have not checked any of these things. How likely is it to be these?

Thank you

KieranMullen
http://360oregon.com

 

9 times out of 10 it is just the o2 sensor but to be sure it is not the cat...get a temp gun and rev the motor a few times and measure temp rise on the case of the cat if it cooler going in that coming out then the cat is good is there is a temp drop or no change in temp on the cat then it is bad

 

Huh?? When a converter fails, you typically can't even hold your hand 3" from the tailpipe because it's so hot. Have a competent mechanic do a backpressure test on your exhaust system and that will tell you if the catalyst is clogging/clogged.

Ryan

 

check my sig.. worked for me, may or may not work for you.

my problem was leaking valve stems/seals causing the cat to get caked. putting the o2 a bit back seemed to give it a clean enough reading so far to keep the cel off.

 

If you have access to scan toll you should check out the parameters of the downstream o2 sensor. It should be between .400 and .800 volts at operating temp.. And as you step on the accelerator the parameters should stay in between those specs. Also If you dont have access to that you can try swapping the o2 sensors around, get the code clear and see if it comes back on. You have a 99 civic. Yes there is a 8 and 80 on it but it 2008 so that wont be matter unless it was recently replaced. Good Luck

 

could be the cat, i remember when they first came out i had a few friends who had to get new cats under warranty with not even 10k on the car. or, it could be the o2 sensors. either way its cheaper to get it diagnosed correctly than to throw parts at it. obd2 cats arent cheap.

 

my obd2 cat was cheap. buy the magnaflow epa, approved obd2 cat. I got mine for 65bucks and it cleared my check engine light.and passed smog

 

How long do those cheapo cats last you?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IP RACING &raquo;</TD></TR><TR><TD CLASS="quote">my obd2 cat was cheap. buy the magnaflow epa, approved obd2 cat. I got mine for 65bucks and it cleared my check engine light.and passed smog</TD></TR></TABLE>

 

May be irrelevant if you have a non-VTEC engine. If you have non-VTEC, the converter is attached to the exhaust manifold. Which brings me to my next point: Honda has a recall for certain years of this body style to replace the manifold/converter due to manifold cracking. If you are a lucky one that has a cracked manifold, your repair bill could be free. Check with your dealer to see.

 

I was apart of that recall the strange thing is Honda Corporate has no history of that being fixed yet my local honda dealer does? But I had that done a long time ago. Perhaps it wasn't really done?

 

Do you have a recall number? I created an account at honda and I could not find the recall with my VIN there even thought I got it serviced. It must have been an under warranty repair that they did for me? Either way I am surprised that honda corporate has no history on the work performed on my car by a honda service station/reseller. All they had in there was the service for my ignition switch.

Thank you

KM


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RyanA &raquo;</TD></TR><TR><TD CLASS="quote">May be irrelevant if you have a non-VTEC engine. If you have non-VTEC, the converter is attached to the exhaust manifold. Which brings me to my next point: Honda has a recall for certain years of this body style to replace the manifold/converter due to manifold cracking. If you are a lucky one that has a cracked manifold, your repair bill could be free. Check with your dealer to see.</TD></TR></TABLE>

 

I was told by a honda tech that if the sensor failed, it would be a different code?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nic &raquo;</TD></TR><TR><TD CLASS="quote">9 times out of 10 it is just the o2 sensor but to be sure it is not the cat...get a temp gun and rev the motor a few times and measure temp rise on the case of the cat if it cooler going in that coming out then the cat is good is there is a temp drop or no change in temp on the cat then it is bad</TD></TR></TABLE>

 

If it is clogged then what? How do you clean a cat out?

KM

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RyanA &raquo;</TD></TR><TR><TD CLASS="quote">Huh?? When a converter fails, you typically can't even hold your hand 3" from the tailpipe because it's so hot. Have a competent mechanic do a backpressure test on your exhaust system and that will tell you if the catalyst is clogging/clogged.

Ryan</TD></TR></TABLE>

 

If you don't want to shell out money, you could try the de-fouler trick. Search and you'll find it. If indeed, the cat is clogged, you should replace it with a new one, or get rid of the catalyst material or with a test pipe.

 

You do mean inserting the spacers? I think that really just masks any problems by not letting the sensor do its job.

How do know if it is clogged?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by angel_i &raquo;</TD></TR><TR><TD CLASS="quote">If you don't want to shell out money, you could try the de-fouler trick. Search and you'll find it. If indeed, the cat is clogged, you should replace it with a new one, or get rid of the catalyst material or with a test pipe.</TD></TR></TABLE>

 

yeah, but the secondary o2 doesnt do anything but test how well your cat is cleaning the exhaust...

if the cats bad, its bad.. why not try to get rid of the code with 3 dollars in parts from autozone?

 

Link to the non fouler trick.

https://honda-tech.com/zerothread?id=1841240

It works good. Only time my check engine light comes on is when I run the A/C on long trips. Dunno why though.

I didn't drill it out completely to 1/2 inch, but it still works. Simply pull it off and look, i think. It should look like honeycomb but way smaller.

 

By performing a backpressure test, you can determine if the converter is clogged. There is no "cleaning it out"; you replace it.

 

CHECK YOUR 02 SENSOR AFTER THE CAT!

 

I have been looking at this post for a while and you have two options.

1. Get a diag done on the O2 sensor with a manufacture specific scantool that can look at the voltages. Hint. the voltage should stay the same at 2000rpm.
Around here they run $100 to $150

2. Have a sniffer test done. if your cat is good you will see no oxygen/o2 from the tailpipe at 2000rpm. $50 bucks

Like was said 9 out of 10 it is the o2 sensor at or after the cat. Not sure what the o2 sensor would cost you.

 

Its the cat, trust me.

 

dont pay $100 to $150 to have your o2 checked, you can do it with a voltmeter...

 

I did not read every post but I read enough to feel the need to post something.
Any way I just wanted to go over how the computer determines a p0420. if you are familiar with a upstream 02 sensor or have seen a a\f gauge bounce back and fourth from lean to rich, this is called oscillations 1 bounce from lean to rich is a oscillation. a good 02 will have 10 oscillations per second, something that can only be seen with a scope. now as the burnt exhaust travels through the cat the rear o2 sensor should show somewhat of a flat signal or no oscillations. when the cat is bad the rear 02 sensor starts to oscillate just like the front one, then the manufacture says when it sees like 3 oscillations per second it says the performance is low or P0420. A clogged cat is caused by a rich condition or misfire that has melted the insides of the cat. if this were the case then you would have several misfires due to the high back pressure and no oxygen left to make another combustion process. its like holding the egr valve wide open (no good) any way the temp test is very accurate in that the whole point of the cat is to heat up the exhaust and burn the left over emissions. it should be 100 degrees hotter after the cat. if it is less then performance is low, if it is the same then it is no good at all. and for who ever thought they should test this with there hand is a DUMBA$$. that's why we have non contact infrared thermometers. it is more than likely your cat but things that should be checked is rear 02 oscillations and fuel trim values to see if it is running rich so you don't toast the next one. Good Luck

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gsrhatch2356 &raquo;</TD></TR><TR><TD CLASS="quote">I did not read every post but I read enough to feel the need to post something.
Any way I just wanted to go over how the computer determines a p0420. if you are familiar with a upstream 02 sensor or have seen a a\f gauge bounce back and fourth from lean to rich, this is called oscillations 1 bounce from lean to rich is a oscillation. a good 02 will have 10 oscillations per second, something that can only be seen with a scope. now as the burnt exhaust travels through the cat the rear o2 sensor should show somewhat of a flat signal or no oscillations. when the cat is bad the rear 02 sensor starts to oscillate just like the front one, then the manufacture says when it sees like 3 oscillations per second it says the performance is low or P0420. A clogged cat is caused by a rich condition or misfire that has melted the insides of the cat. if this were the case then you would have several misfires due to the high back pressure and no oxygen left to make another combustion process. its like holding the egr valve wide open (no good) any way the temp test is very accurate in that the whole point of the cat is to heat up the exhaust and burn the left over emissions. it should be 100 degrees hotter after the cat. if it is less then performance is low, if it is the same then it is no good at all. and for who ever thought they should test this with there hand is a DUMBA$$. that's why we have non contact infrared thermometers. it is more than likely your cat but things that should be checked is rear 02 oscillations and fuel trim values to see if it is running rich so you don't toast the next one. Good Luck </TD></TR></TABLE>