vcantrell

Alrighty.. so here's the issue. I'm trying to sell my 2005 Civic EX, and in the state of TN, they can't register it without passion an emissions test. One of my fuel injectors was leaking fuel all over my engine for a few months there and now, even after it's fixed, the P420(or something like that) code for cat below emission threshold won't go away.

Instead of putting $300 into a new cat... my fiance has a 2004 civic DX with a working cat converter. Can't I just pull it out and put it in mine and everything should fine and dandy?

A friend of mine told me that I'd have to cut it out of hers and weld it into mine.... but everything I've read says that on these civics, it's just some bolts. Any thoughts?

As far as emissions for her car goes... her engine light has been stuck on due to her downstream oxygen sensor for the past 100,000 miles and we are registered in michigan so we don't have any emissions tests. ever.

Will this work??

Thanks,

Vince

MelJ

It might, but be warned that if something killed the CAT in the first place, it's going to do the same thing to the one you swapped in. You should figure out what's going on before you start hacking at stuff. Have you tested the o2 sensor on/behind the catcon? I know in NY it's illegal to take a catalytic converter off another car. I think this may just apply to junkyard cars, but if I were you, I'd check. You're playing with fire trying to switch catcons and selling the car. Just be careful.

vcantrell

lol I put in the first post why the cat went bad.

my alternator went bad and i drove the car dead a couple times last fall. because of this I killed one of my fuel injectors causing it to literally pour fuel over my engine every time I ran it. I didn't run it much, but apparently I ran it enough that the leaking fuel completely ruined the Cat.

I've had three different mechanics tell me that it's the cat. There's a special code for the 02 sensor, and that one isn't going off... so I have to think that it's the cat.

MelJ

What I was getting at was if the car was running rich, that could cause an issue. Your injector had a leak, I understand that, unless that's what you meant. My car threw the same code but hasn't come back on even after 3 months of running the drive cycle. Heh. I don't remember exactly what I did, but I think the o2 sensor on the cat got funky or something.

xRiCeBoYx

iTrader: (22)

here's the thing between your fiance's dx and your ex: they have 2 completely different exhaust systems. Your car is located underneath your engine, on the tail end of the down pipe. Your fiance's dx has the cat right off the exhaust manifold.

Another option you can do is find a universal cat for cheaper and find an exhaust shop to cut out the old one and weld in the new piece.. no idea how much that would run you tho.

vcantrell

dang... I went and checked my car and she checked hers (facetime... lol) - You'll have to forgive my ignorance here... exhaust isn't something I've really messed with.

From the back of the car we both have the exhaust obviously... and then from the side (facing the back but from the inner part of the wheel axis) there's another manifold looking thing.. or something. The picture below is of a newer car, but it's the same parts and location as ours.



We have both of these in the exact same location on both our cars...

Further down the line is my cat, towards the front of the car after the bend in the pipe... but she doesn't have that. Her pipe goes all the way to the front and up into the engine.

Am I missing something here?

OH, and I just realized hers is an HX, (that's the base model right? Whatever the base model is.) - I just read that the DX wasn't available for 2004 civics... that it became special edition. Whatever the base model is, that's what she has.

nsxvtec

Yes. You are missing something.
What he is trying to tell you is that your cat in under the car, just around the shifter area. Her cat is built into the exhaust manifold, right up front at the engine. Harness locations for o2 sensors are different also. There are replacement direct fit cats available that will bolt right up that are not as costly as 300.
Do a quick search on line for replacement cat converters.
You will find many places like this:-
http://www.familycar.com/autoparts/h...converter.html
where you can get various versions.
Just a quick clarification, in that your picture shows the resonator and the muffler which has nothing to do, location wise, with what you are trying to deal with, which is the cat.

TreeFortRichard

Reasoning behind no CAT swapping..fyi...Is because you and 11 friends could use 1 CAT for 12 cars, inspecting 1 per month..and at any given time 11 of them are bad...By not permitting swapping it means it's more likely that cars on the road have working CATs

vcantrell

Well yeah I understand the reasoning behind it... I'm just kind of annoyed because there's no reason for me to have one, and yet I'm still spending at least $150 to put one in for a buyer.

sdaidoji

iTrader: (1)

you could also try to see if you can find a lower mileage one in a scrap yard...
or try online, like E-bay, or maybe here
https://www.hondapartsonline.net/honda-civic-parts.html
or maybe here
http://www.car-part.com/

sdaidoji

iTrader: (1)

Also, just as info, so no one gets the wrong idea. This is for a 6th gen, so some differences might apply, but overall configuration seems to be same.

Added this to the sticky in the DX/LX to EX FAQ sticky, BTW

(thanks to trustdestruction on hondacivicforums)
DX/LX/CX/HX Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)



The headers available for 96-00 Civics are only made for Civic EX%u2019s (except for one made by Magnaflow, but I am not going to talk about that because it is not as good as an EX header). Civic EX%u2019s have a regular exhaust manifold, with the catalytic converter located directly after the exhaust manifold.

If you have an aftermarket catback exhaust on your DX/LX/CX/HX, then chances are, your catback looks like the one in the first diagram, but has a short removable ~16" section of piping, located where the catalytic converter is on the EX layout. In this case, when you get the EX catalytic converter, you just replace that short ~16" pipe with the catalytic converter. This ~16" section of piping is essentially a test pipe.

EX Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)



There%u2019s two things you can do - a wrong way and a right way.

The wrong way:
Install the EX header onto your car, and leave the catalytic converter completely out of the equation.

This is a bad idea for a few reasons:
1. It is illegal, and if caught, you will be penalized.
2. You will throw a CEL (check engine light) and the car will run in limp mode (limited power, bad gas mileage lower rev limiter, etc.) because the secondary O2 sensor will think that the catalytic converter isn%u2019t working, or you may not be able to hook up the secondary O2 sensor at all.
3. Instead of CO2, NOx, and H2O, your exhaust will spew out hydrocarbons and poisonous carbon monoxide gas.
4. You will fail emissions/smog/inspection/etc.
5. A test pipe gives you only ~1WHP over a high flow catalytic converter. 1WHP isn't worth breaking the law and/or failing smog.
6. You will be polluting our air even worse than it is already being polluted.

The right way:
Convert to the EX exhaust layout by installing the EX header, installing an EX catalytic converter located directly after the header, and using an O2 sensor wire harness extension to relocate the O2 sensor to it%u2019s new location on the EX catalytic converter.
You can convert using bolt on parts designed for an EX, or you can cut and weld the exhaust parts together as needed. You can have your original catalytic converter cut off and welded directly after the header if you want. The advantage to bolt on parts is that anyone can do it themselves with simple hand tools, and different pieces can be taken apart in the future if necessary.
Any method will work, as long as the finished product has this layout:

Converted Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)



Items needed:
-EX catalytic converter
-EX header (a.k.a. exhaust manifold)
-O2 sensor extension wire harness
-EX aftermarket or stock catback exhaust (aftermarket DX, LX, CX, HX catback exhaust will work if it has the removable ~16" section that I mentioned earlier. If it doesn't have that section, the only thing you can do is cut the piping and weld the catalytic converter to the mid-pipe of the catback exhaust.)

nsxvtec

1. Fix it and show this in your price and ad.
2. Sell it as is and include this fact in your price and ad.
.........Done........ Finished.........

xRiCeBoYx

iTrader: (22)

This.

vcantrell

I bought a universal cat for my EX off amazon... it's universal so it may take some welding... but it's magnaflow and it got decent reviews.

It's brand new and it appears to fit where my current cat is...

What I'm worried about is... the p420 code.

That can technically be anything right? The mechanics told me that it's more than likely the cat since I was pouring fuel over my engine I probably ruined it... and there's a separate code for the 02 sensors... My question is...

what else could it be if the light comes back on after the new cat is installed? If we know it's not the sensors since they have their own code... any thoughts?

MelJ

The p0420 can possibly be the secondary o2 sensor or the cat itself. Like the sensor could be funky. That one only monitors the catalytic converter. It compares signal from the one pre cat. If the voltages are too similar, it'll throw a code. The sensor itself could possibly be bad and give a false reading, thus throwing the code. The only way to know for sure is to run the monitors for testing the catalytic converter. I don't remember the tests off the top of my head sadly, but I went through and did them and my CEL never came back on. I think you have to drive to 55 mph, slow down without applying the brake to like 25 and then speed up to 40 or something. I wouldn't trust that method lol, but I'd suggest looking it up online to verify that you have fixed the problem.

vcantrell

when you say run the monitors for testing the cat... is there any chance you may know where I could find this procedure? I googled and searched and didn't come up with anything concrete lol

Does anyone else know maybe?

Thanks by the way

MelJ

I have shop today, so I can get the stuff for you if nobody gets back to you. I'll copy and paste it here later on today.

MelJ

Here are the steps. Sorry if it's a little messed up in terms of organization. I just copied it:
1.Reset the ECM/PCM (see HOW TO RESET THE ECM/PCM ), then continue to step 2 through 5 to reset the readiness code.
2.Start the engine. Hold the engine speed at 3,000 RPM with no load (in Park or neutral) until the radiator fan comes on.
3.Drive for about 10 minutes without stopping on a highway or freeway. Your speed can vary.
4.With the A/T, CVT in the D position, M/T in 5th gear, drive at a steady speed between 50-62 MPH (80-100 km/h) for 30 seconds.
5.Repeat step 4 three times. Between each repetition, close the throttle completely for 1-2 seconds. If the engine is stopped during this part of the procedure, repeat steps 3, 4, and 5.
6.Check for a Temporary DTC with the HDS or a scan tool.

vcantrell

Okay awesome... thanks!

So basically... idle it at 3k rpm till the fan comes on. - get on the highway and drive at 55 for 10 minutes. let off the gas for 1-2 seconds. drive at 55 for another 10 minutes and let off for 1-2 seconds. - do this three times and I'm good?

That seems like a lot less time than you said earlier; like... you said let it flow down to like 20 and then go again right? Just double checking~

MelJ

Lol. Yeah it does. My test was different since I have a different generation Civic, but the process was pretty much the same.

vcantrell

OK awesome! well thanks so much for your help!