Mr.Civic

Hello everyone,

I need some help in finding out the problem with my car (2000 Honda Civic SE - D16Y7 ). My check engine light is on, and is trowing a P0420 code. Looking at a DTC Library, it says "Catalyst System Efficiency Below Threshold Bank 1"

Reading on the forums some say it could be one of the O2 sensors or the catalytic converter. I decided to do a small test by unplugging the top O2 sensor and do a SCAN on my Autel code reader, which gave me the P0135 code only, meaning "O2 Sensor Heater Circuit Bank 1 Sensor 1". I plugged the sensor back in, and that code goes away, which ensured me that that sensor is not faulty.

Now, my question for the more experienced, I found these diagrams.





Looking at the diagrams, it shows that there is another catalytic converted under the car with 2 more sensors, is this correct? or is there only one catalytic converter which is displayed on diagram 1.

I'm not sure on which one needs to be replaced. I need to fix this problem soon, as I need my plate sticker, and in order for me to get it I need to get an e-test done to the car as I'm in Canada, and they're pretty strict about this kinda stuff.

Any information or help in this matter is greatly appreciated.

g.r.crx

yours is a y7 so your cat is in first picture, second one is for y8 motor. your cat is part of the header.

Former User

P0420 generally means that the cat needs to be replaced. Occasionally, the code can also be thrown by an exhaust leak. A faulty O2 sensor generally won't throw the code.

Do an ignition system tune before you replace the cat so you don't soon destroy it again.

Mr.Civic

Okay, thank you. So the cat is attached to the header.. now I took the heat cover off and found a surprise, I took some pictures with my iphone.. it looks like the top is cracked and has been fixed before, could this give out the engine code?..


https://www.dropbox.com/s/yq284nh4m9...2010.17.33.jpg
https://www.dropbox.com/s/krmryzetx9...2010.17.53.jpg
https://www.dropbox.com/s/3w5vdjag0d...2010.17.46.jpg

Former User

Replace the header and then go from there.

Mr.Civic

Could the code be produced by a leak in the exhaust manifold?.. I just posted some pictures in my post above.

Also how can I perform an "ignition system tune"..

P.S. Apologies if my questions are somewhat n00bish.. it's a learning experience for me. So I appreciate all the input you guys can give me.

Mr.Civic

Thank you.

94EG8

Yes, however there's not much you can do with it besides replace the manifold, and the cat is part of the manifold (some aftermaket units will separate, the OEM unit does not) Those manifolds were notorious for cracking right there. You may or may not be able to remove the primary O2 sensor without ruining it, sometimes they come out, sometimes they break off or strip the threads.