HiYa, I got a 1998 Accord with a 2.3/ 4 cyl . with 108K. The "engine" light just came on for the first time. The OBD "2" scanindicated a "0420" code/= catalyst efficiency below threshold. Time for a new one I guess?Question #1.Does thecomputerautomatically "activate" this code at a preset milage from the odometer or is this an active sensor system telling me the converter is going bad? Question#2. Honda stresses to use an OEMHonda only converter V/S an Autozoneor generic one from the local muffler shop. Is there any difference concerning engine operation?

Thanks, man.... I love this site!

 

The measurements from the O2 sensors can throw that code, it's an active sensor. If you get an aftermarket cat you have to make sure that it can produce the same results as a honda one or you are going to get a funky reading and possibly a check engine light. If you live in an area with emissions testing I'd probably advise you to stick with OEM.

 

P0420 code is produced by the ECU monitoring the performance of the O2 sensor voltage for the sensor behind the catalytic converter. The voltage trace should be almost smooth w/ few changes in voltage if the converter is working correctly. The ECU counts "zero crossings" (not really zero but a mean value) to gauge the converter performance. If the number of zero crossings is comparable to the O2 sensor ahead of the converter, it sets the code P0420. This code can be falsely set by air leaks into the exhaust ahead of the catalytic converter; cracked exhaust manifold or leaking exhaust connection.

Check the exhaust system carefully for leaks. Also check the conveter for rust holes and try to shake it to see if the converter matrix is loose. If it's loose, you'll have to replace the converter.

OEM or aftermarket? The OEM is a very good product, but you want to be absolutely sure it's the converter that's causing your problem. Only individual can decide whether the premium for an OEM converter is good value.

I had P0420 on my 99 Subaru Forester and after 6 months of resetting ECU and checking converter andexhaust system, I eventually bought an Eastern Catalytic aftermarket for < 1/2 cost ($240) of OEM. It has worked fine for 6 months now. Welding a "universal catalytic converter" into your exhaust might seem even cheaper, however the welds will corrode at a horrific rate compared to the SS410 the converter and pipes are made from. The OEM and aftermarket use better welding consumables and weld corrosion is better, but still much worse than the parent metal around the welds. Check convertergeek.com for aftermarket converters. I bought mine on ebay, but they appear to have similar prices and a better selection.

I would reset the ECU by pulling the BackUp fuse for 20 secs. This will cause the CEL to disappear, but it will return if the fault is true or you have an exhaust system leak. You may want to do this several times and check everything very carefully. If you have an Obd2 scanner that can monitor the aft cat O2 sensor trace, you can see the voltage trace and understand my explanation above.

good luck

 

If it is the cat and you've got to replace it, I'd recomend a Catco high flow cat. I've got one and I like it. If I remember correctly, they say they will still pass emision testing. As for performance gain, I couldn't tell you if there was any, I put it in the same time as my catback exhaust system. I'm not showing any engine light because of the high flow cat. I got engine codes for other reasons, but not that.

 

http://www.autopartswarehouse.com/pr...ytic_converter

hope this helps..

 

62Maxx


I have the same problem a few weeks ago. I got the code P0420 also and I replaced the Oxygen Sensor that is connected to the Cat. Convertor. I been driving it ever since and the Check Engine Light did not go on since, I would say change the 02 Sensor first because that's the cause. I spent a $140 for a OEM Honda one. Did the work myself, pretty straight forward. I would recommend getting the O2 Sensor socket remover from Autozone or PepBoys. It Fix my problem. I have a 98 Accord Ex 93K miles 4 Cyl.

https://www.hondaaccordforum.com/Che...m_77375/tm.htm

 

I recommend making an appointment with a shop with a 5 gas analyzer and a scanner so they can monitor the post O2 sensor and also get gas readings to see if your engine is burning too rich or too lean where a good cat still would not work properly, TEST then purchase what they say.

Sorry, I didnt pay close attention, are you making some lengthy drives too, the O2 monitor will take some real time to run depending on your driving habits and may not run on short trips.

Go to MOTOR magazine archives (back issues) and read up on Honda LAF Sensor testing, yours is an LAF, not an O2??????, Sep and Oct 1999.

 

I stay away from aftermarket cats. They are good for performance, but often times on most newer vehicles the ECU's value range is so "tight" that aftermarket cats, although they work at reducing emissions, will still throw a P0420 because the ECU doesn't see exactly the right values.Many times, if a P0420 is not fixed with an aftermarket cat, an OEM is the only true fix.

As above, make sure everything else has been ruled out, and that the other vehicle systems are up to spec so the new cat doesn't suffer.

 

I would NOT buy a new o2 sensor. P0420 is not an o2 sensor code. If you want a cheap(about $5 to DIY)way to possibly get the code gone and maybebe able to pass emissions, try the "defouler trick": http://www.honda-acura.net/forums/sh...d.php?t=206101
I am not telling you whether or not this would fix your problem, but it is cheap and fairly easy to do.