kcanoy

So here's my story. I got a P0420 with a check engine light a while back (1 to 2 months ago) when my car was back firing due to a bad distributor. Distributor has been changed and the back firing ceased but I want to know what to do next. Should I change my CAT converter or should I change the O2 sensor? Is there any way I can check that the CAT is clogged? Which O2 sensor would need the change? The car still seems to be running fine and the CEL tends to turn off but then goes back on every once in a while? HELP NEEDED! Didn't want to post hack on someone else's either so sorry if all you guys are tired of seeing this topic

lazlong

Reset the ECM/PCM by pulling fuse #6 in the under-hood fuse/relay box for 10 seconds while the ignition is off. If that doesn't make it go away then you need to replace the cat. Cats go bad over time, they're designed to do that. It's usually not the sensor.

MelJ

I know this thread is old, but my car recently threw this . Not too happy about it because I just finished replacing my axle seal without an issue. If my problem turns out to be the catcon, should I just get an OEM one and have a shop replace it? I'm gonna start troubleshooting either tonight or tomorrow.

lazlong

Usually (about 80-90% of the time) it's the cat. You could try replacing the sensor(s) and if that doesn't fix it replace the cat. You should replace the sensors when you replace the cat anyways.

If you wanna pass emissions, then yes, go with OEM. Most everybody has had no luck with the cheapy aftermarket ones.

Squeeken

MelJ, I just passed California smog today after changing out the catalytic converter on my 2001 Honda Civic LX due to a P0420 code. I have done extensive research on this problem and I can tell you that the P0420 code is almost certainly being caused by a bad cat. If one of your O2 sensors were bad it would cause an O2 code to be displayed by itself or in addition to the P0420 code.

I replaced my Cat only, and not my O2 sensors, and that took care of my problem.

If you have a scan tool or can get your hands on one, you can hook it up and monitor your O2 sensors to see if they are working properly.

Read this...

http://www.aa1car.com/library/p0420_dtc.htm

It has some excellent information on the P0420 code.


Read my thread...

https://www.civicforums.com/forums/4...-civic-lx.html

I have been dealing with the P0420 code for the last year and a half.

I strongly encourage you to by an Original Equipment cat from Honda if you want to pass smog. I bought mine at HondaPartsNow.com for $200 less that what my local dealer wanted. They are operated by Robertson Honda in North Hollywood.

Good luck. I hope this info helps you out.