radub

I have a '96 Civic CX. So a couple weeks ago I had a new exhaust system put in - muffler, exhaust pipe, etc. Shortly after that my check engine light went on and I had the code read - P0420. Is it possible that the mechanic, while replacing the exhaust system, somehow messed with the rear oxygen sensor and cause the check engine light to go on? Or would it definitely be totally unrelated? Thanks for any and all help!

ezone

Explain what "etc." entails. What all else was done?


Oh yeah, here we go. Blame the mechanic just because he touched the car weeks ago. WHY would you think that?
Trust issues? Suspicious? Paranoid?
I suppose he made the tire on your other car go flat too.







I heard he installed a "self destruct" controller in it, set to go off when you are far, far from home.
Far from civilization.
B.F.E.
Out of cellphone range too.
In a freekin blizzard.


With video.
You're welcome.



Does it LOOK like someone messed with it?
Why don't you direct your question to the person that did the work?
Don' be scurred......I'm sure some of us out there aren't packing heat.


Probably unrelated.
The car is almost 20 years old, with a zillion miles.
I suppose you are in the rust belt too.
Why can't it have an actual problem here?
Face it, **** happens. It's a machine, it can break.

The code says it probably needs a cat, not a sensor.
If it had a crappy sensor, it would probably set codes for that sensor , not a cat code.

baws187

I would think it is possible because it goes in the exhaust. I just got this code I am hoping its due to seafoam in the gas a pint of it.

ezone

Then clear the code, run the gas tank to damn near empty. Refill and see what happens.

Sometimes the first time a cat code comes up and gets erased, it might take a while before it comes back. But the cat code almost always comes back sooner or later.

baws187

I erased it right away came on again I guess we will see when I run the gas out. I am hoping I dont need a cat. I was going to put a new 02 sensor but from reading seems like its probaly the cap. If I were to run a test pipe with the 02 sensor in it will it throw a code?

ezone

Yes, because there would be no cat at all.


There are ways to get rid of the code though, but are not emissions legal.


*hugs a tree*

Stock 99

I seafoamed the gas in my '99 (6th gen) twice 3 years ago and 2 years ago and my car has never thrown any codes.

ezone

Blame your mechanic for that!

Stock 99

but....I am my mechanic.

baws187

I saw there looked like a whole to put sensor in. I use an elm 327 obd2 Bluetooth reader and I use the torque app. Best 15 dollars spent on amazon ever real time data. I can clear it but when you clear it resets thedrive cycle if those cycles aren't met you cant pass emissions in PA. Thanks for any help.

ezone

The code and data reader app is nice, but if you don't understand how the car itself works, it is of only limited value.
What exactly do you want?

This is pretty simple:
If the P0420 code comes back, you need a cat to fix it.
If you have to pass an emissions test in order to drive it, you need a cat that will pass the test.

I'd recommend a cat that is from Honda, or California CARB certified compliant. These are most able to last the longest. Anything less is a crapshoot, and you get what you pay for. Many cheap cats don't even make it past the warranty period.

A 'test pipe' is not a cat, and you cannot use it to pass a test.


Right.

baws187

Well test pipes are alot cheaper and I know a guy who will pass it as long as the cel isnt on. I thought they had a hole for your o2 sensor. I want cheap speed and a of course to get my cel off. Carb will hurt performance.

ezone

Because they are not a catalytic converter.

Good luck with that.
I know I wouldn't risk my license and livelihood (and that of the shop I work for) for people that don't play by the rules.
Probably.

A test pipe alone can't keep the light off, and you won't gain an ounce of performance.
You mean a cat, and your assumption is incorrect.

baws187

I meant C.A.R.B. the California emissions. That hurts performance more then cat so actually your assumption was wrong. When I looked the code up it said bad catalyst in bank one. I thought that meant the o2 sensor upstream was bad.

ezone

It seems you are confusing the difference between California emissions standards, and a CARB certified part.

A properly working, correctly sized cat does not restrict flow, nor engine performance (in the gearhead sense of the word). It does not matter if it is CARB certified or not.

If you want to have some assurance a new cat should work well and last a fair amount of time, Californias vehicle emissions standards are more stringent than the Federal emissions standards.
They also dictate their own rules for warranty coverage for many items, which is far longer than the rest of the country.
A cat that is CARB certified has a much better warranty than a run-of-the-mill cat you get for cheap in most other states. (If you read the notes with those cheap cats, they state they are not legal to sell in California for OBDII vehicles.)
A CARB certified cat is of higher quality (precious metals and substrate components) than an aftermarket cat you buy elsewhere in the US, that's the only way they can get them to last throughout the much longer warranty period (typically 5 years for a CARB unit IIRC, as opposed to one year for a Federal unit.).


If you don't need the cat to last, feel free to get the cheaper options. Many cheap cats can't keep the computer happy for very long.

P0420 means the cat failed its self test for efficiency, to store and release Oxygen.

It has nothing to do with the hot rodders meaning of the word "performance", unless it gets clogged or the element is broken causing a restriction.





Have a great day.

mikey99civicex

im sorry to but in im new at this site how do you create ur own post?

baws187

I was under the impression that a test pipe is less restrictive. I also assumed the carb ones were even more restrictive. With those assumptions I figure test pipe would free up a few horsies. I thought since they had the hole for the o2 sensor. I have 103k on it runs good so I do want something that will last. I was gonna do headers back with some descent exhaust. I love my 00 civic ex.

I appreciate your help. Ezone

ezone

Locate the area you wish to post in, such as this path:

Honda Civic Forum > Honda Civics by Generation > 6th Gen > Mechanical Problems/Vehicle Issues and Fix-it Forum

Then find this button near the top of the box .

Type away!

ezone

YW.


You have no idea how much snark I wanted to put in my last reply LOL.



/at work
//short fuse
///idiots galore
////is there a full moon?

sdaidoji

iTrader: (1)

whatever you do, the ECU will know that there's no cat in there, they meow to each other.
when you reset, the ECU will need to run for a time (around 100 miles) to be ready for the emission test. Do you think the CEL will come on before the 100miles? yes. they do.

baws187

I was hoping ebay had a way to trick it so I could run a straight pipe.

ezone

There's a trick, yes..
And it's really stupid simple (and dirt cheap) once you figure out what it is.
It's done by using other car parts sold for an entirely different purpose.

You could just use what I'm talking about without the test pipe too.
But it won't pass a visual inspection at emissions testing.
Neither will a test pipe.



/hugs more trees

sdaidoji

iTrader: (1)

search foul plug

baws187

Are the holes in the test pipe where you screw the fouler in?

ezone

Use them to space the rear (second) sensor out away from the pipe slightly.
You can do this to the bad cat you have now. No test pipe needed.
I can't tell you how to do it. Defeating your emissions system would be unlawful.

I did NOT just tell you this.