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My first post but hope to have many more, I need to figure this out so it doesn’t cost me a ton of money and aggravation. As you can see from the Topic I have the dreaded catalyst system below threshold P0420 code. I have replaced the downstream sensor already. From what I have found on the internet it seems like it’s the CAT! I don’t have the cash to buy a cat and was hoping it was just the upstream sensor. Can anyone tell me how to find out if the upstream sensor is bad or how to really tell if it’s the cat.The car gets around 35 mpg, the cat is not rattling or making any noise. Any help would be appreciated. I also have a friend’s OBD to hook up and analyze.

My second question, I also have an issue with the power locks, intermittent wipers, dome light and the A/C does not work. I read on the internet that this is the Control Unit located under the dash with fuses and relay's. This control unit has a board integrated in the panel that controls all these items as I understand it. I am very mechanical but I am a little low on cash at the moment. Again any help would be appreciated. Thanks in advance!

Last but not least the car is a 2002 Honda Civic EX 1.7 Automatic

 
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Wow, 117 views but no one know"s? Not what I expected.

 
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That just means its 117 people that don't know what to tell you. Prolly some spambots in the mix, too.

So, if its any sensor, it'd be your downstream, not upstream. That's the one that monitors cat efficiency. You can get rid of the code by using a mechanical o2 simulator. I'd link you, but I'm on my phone at the moment. That'll just pull the o2 sensor out of the exhaust stream to make it read falsely within spec.

 
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Okay did the non fouler today and so far its working, ran around for 45 mins and engine light stayed out. Had OBD hooked up to and not sure what I was looking at but the 02 sensor 11 showed lower readings then 02 sensor 12 did when not on the gas and just the opposite when on the gas so I guess all is good rite? Hopefully someone will chime in.

 
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The cat code is for the cat. Very few other things will cause it. Exhaust leakage is one thing that can cause a false cat code.

You need to figure out if the cat was killed, or if it died a natural death.
If it was killed, that needs fixed before another cat goes on.
You can kill a brand new cat in only a few minutes if there is something drastically wrong with the engine and the way it runs.

If you can't afford the cat, don't waste coins on O2 sensors it doesn't need. 99% of the time a bad O2 sensor will set a code specifically related to the sensor itself.

The nofouler trick only hides the cat problem from the computer. The computer will be the judge.
It won't pass a visual check during an emissions test.


*hugs a tree*

 
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Ezone,

I agree with you 100% but can you tell me how to figure out if the cat is bad or not? The vehicle has 170,000 on it now and runs smooth, will the non fouler pass a vehicle inspection? Im trying to get the car on the road and rite now I only have 30 day tags to get it threw inspection.

Have you ever put on a brand new 02 sensor that was bad? I talked to the counter guy at Advanced and he said I could bring it back if the code stays.

 
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Not necessary.
The computer already checked it for us.
As long as there are no exhaust leaks between the engine to about 2 feet past the cat, we can assume the P0420 code is not false.
Again: If there are no exhaust leaks, that cat is bad.



Non-foulers should fail a visual inspection (tamper).
I guess it all depends on your inspector though.

And it depends on your areas emissions testing program.
They are not all the same.
Some might require looking at the car and/or sniffing the tailpipe smog, others might only plug in to the diagnostic port and collect data.


Maybe? Not that I recall on O2 sensors specifically, but I avoid parts store electricals as much as possible.

I have seen plenty of O2 sensors installed that were absolutely not right for the cars, the computers did not like what they saw and caused problems that way. Same for MANY other parts form the aftermarket. Same for dealers. Same for techs. It takes a human to replace the wrong parts.
Again, the computer is the final judge for many of these things.

Along the same lines: NEW stands for Never Ever Worked.
It happens even with factory parts.

What does that have to do with the cat code?
Is the car now setting codes related to any of the O2 sensors?

Do you still have the old sensor? Did it cause any sensor codes?

 
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What does that have to do with the cat code?
Is the car now setting codes related to any of the O2 sensors?

Do you still have the old sensor? Did it cause any sensor codes?

Its all making sense now and I really appreciate the response from you Ezone.

The old sensor had the 0420 code so I purchased a new sensor thinking or atleast hoping the code would go away, now I believe what you are telling me which was rite in front of me the whole time. The cat is bad and it must be replaced thats what the code means, lol.. I do have the old sensor but I doubt they will give me a refund for the new one but maybe an exchange but both sensors are good Im sure.

Now looks like Im in the market for a new cat, would you say this would work out for me?>>>>http://www.jegs.com/i/Magnaflow/642/51354/10002/-1

 
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Hi i might sound like a fool but i just joined the forum cause i bought a 1997 honda civic coupe and it has a leak in the power steering mechanism. It is leaking at the back of the engine maybe some hose or some part is missing is what the mechanic says. If someone couhelp me out it will be really nice you can contact me on my email id gargutkarsh@gmail.com n i can send pics of the leak. Thank you.

 
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Not if you are in California. The cat must be CARB approved (or something to that effect.) See an emissions specialist (smog tech).
Not if you are in a state that models their emissions program after Californias. Same as above.


If all they do is scan it for codes and you think you can get away with it, leave the nonfoulers on and hope they don't look.

 
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Ezone,

Thanks again for your help. I have a buddy that has a body shop with just about everything to replace the cat, he actually has a Civic that is basically just going to be a parts car. Im (thinking) of taking the cat off it and using it. Would that be a wise choice or not? He has everything so I could just cut off both cats and install the one from the older Civic and weld it up no big deal but I dont know if the puter will like it or not, can I get you to chime in again for your opinion? Im in Maryland but Im not sure about the way cat inspection go down.

 
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If it is an identical car and identical cat, just bolt it on and give it a shot. (I can't tell if bolting would be easier than welding from here.)


More: Is the parts car driveable now? Does it already have a cat code?
Looking for an easy reason to rule out using the cat from the parts car before going to a lot of work to change it. I hate wasting effort.


Can you find out more about the things they check during an emissions test there?

 
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I just got done rebuilding my d17a1, I too got the dreaded P420 smoked out code. =P The way the ecu works, if it’s tell you code specific it’s pretty much telling you in English what’s going on. So in my case living in California, I either have to go with a California Approved Catalytic Converter, or go with a OEM from Majestic. Something to note about California. If they inspect the cat and suspect it’s an aftermarket and doesn’t have a CARB number you just wasted a ton of money. Also the aftermarket manufactures don’t have super high standards like OEM Quality. The life for aftermarket cats are something like 3 years, and then they fail.

So on this note, I cleared the code last night but doesn’t mean it’s lurking in the background ready to go off again.

 
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I have found this supplier and think this is a good deal, tell me what you think of the price and or quality.

http://www.autopartswarehouse.com/sk...gs+Best+Seller

Im going to check and see if the parts car currently has any codes and thats good advice, the car is an older Civic not sure of the year yet and that's why I was mentioning the cut and weld part.

I will keep you posted.

 
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I would hope the donor is at least the same generation/body style as yours. I really don't know how much difference that would make though.


Check your local regulations.
That's not a California approved unit.
If your regs allow using that unit, it probably won't last all that long--- if the computer doesn't hate it right off the bat.

It's cheap for a reason.

I hate watching a cheap customer go around and around with cheapo cat(s) that can't ever make the computer happy. They can spend far more than it would have cost to just install the right one the first time. (This applies to far more than Hondas.)



Even more fun is seeing that the muffler shop can't tell which cat to replace, they replace the one cat that hadn't set any codes yet and stick in a cheapo cat that sets codes right away. Now it has codes for ALL the cats. (GM V-6/V-8 pickups with dual cats comes to mind here.)

 
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Recommend a catalytic converter. Probably not the oxygen sensors, or it would have coded for them.

 
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Sorry been a little busy with things around here and just took the car threw vehicle inspection to get the permanant tags, failed on just a few things, rear running light, rear strut (leaking) did not catch that myself, and one of the studs was a little boogered up, also they got me on the daytime running lights not working. I replaced the strut, replaced the rear bulb, replaced the stud and then discovered something when I was trying to get the day time running lights to work, my car is a Canadian built car. From what I found out the day time running lights on a US car are just the low beams but on my car I actually have a bulb built into the head light. Correct me if Im wrong but thats what I have found out. Not sure if thats a good or bad thing but so far its a bad thing cause I cant figure out where the damn relay for the day time running lights is hiding. I found the three relays behind the glove box but not sure if that is them or not, called Advanced today to get the relay and they said they dont show one. Someone please chime in and tell me something about what my problem is, everything works on the car except for the DAYTIME RUNNING LIGHTS! my temp tag runs out Friday!

I also changed out the multiplex unit above the gas pedal which made a few things work again, A/C compressor, Dome Light, Intermittant wipers, Power Locks and the little buzzer for when the key is in the ignition and the door is open and it made the brake light go out on the dash. I changed the multiplex unit before I had an issue with the running lights. the running lights have never worked in the short time I have had the car. I will be checking the connector at the bulb for the running lights tomorrow when i get home from work to see if I have juice or not. Please help!!

 
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A Canadian BUILT car is not the same as a Canadian MARKET car. Tons of US market cars are built in Canada.

US market Civics didn't have DRL's until......2006? (*shrug*)



What is your car? Where is it from? Do US catalogs recognize your VIN?

 
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02 Canadian Civic with DRL would have a DRL indicator light on the gauge cluster, a DRL control unit under the left side of the dash, and would use the normal headlight bulbs. No separate light bulbs.

 
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Its a 2002 Civic EX 2 door coupe 1.7. Ok then that means I have an American car I guess, really doesnt matter to me I just want to get the DRL working and have checked all the fuses, #3 and #12 on drivers side fuse box, checked and replaced fuses #15 and #17 in the engine compartment fuse box as well.

Can you tell me which relay makes the light work and where to find it?

 
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Again: US market cars don't have DRL.

 
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Your 02 doesn't have DRLs.

 
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PM the VIN to me, let me check on the Honda site real quick.

 
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Im confussed, I see the bulb and see the wire but they dont work and it failed inspection for them not working. Im going to get a pic real quick and post.

 
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brb, Ok I will.

 
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Bulb #6 is a marker light. #194 bulb available at any parts store.
Comes on with park lights. It is not a DRL.

 
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Then it must just be the bulb! (light goes on) hehehehe

Thanks Dude, will pick up two tomorrow. Tried taking headlight fixture out earlier but was dark and cold out and gave up after the other stuff I did on the car, two bolts at top and seen on Majestic there was another at the bottom I didnt see.

 
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You would have to take the bumper cover off to remove the headlight housing IIRC.

Those sockets WILL come out without all that work.

IF you can't reach the socket from the engine compartment, try pulling back the plastic inner fender liner and reaching through in front of the tire.
(I don't bother to remember the many different cars. I have to see it and decide at that time.)

 
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Ahh another wise choice, will try both as soon as I arrive home. Thanks Ezone!

 
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Here is my light as you described it.