hey guys
my 98 accord check engine light on the other day. i took it to autozone get the trouble, which is p0420---the catalyst system efficithcy for bank 1 is below threshold for the current engine operating condition.
what does this mean? what should i do to get rid of the check light? i try to reset the ecu. it will go off for one day, then second day come back on again. does that mean it's time to change oil? this really bothers me, so give me some ideas, thanks.

 

I may not know much about Hondas, but that exact code on my car means the passenger side o2 sensor isnt responding correctly. If your car is setup the same way as mine, bank 0 is the driver side, and bank 1 is the passenger side, and thats the side with the bad o2 sensor. If you want to test it, swap your driver and passenger side o2 sensors and see if the code switches to bank 0 being bad.

 

You don't have driver & passenger side sensors. Even with a V-6 the banks are front & rear because the engine is mounted transverse. P0420 is used for the catalyst in a 4-cyl, even when the 'other bank' doesn't exist.

The downstream O2 sensor measures how good the cat is working. That's the sensor down on the exhaust, sorta underneath the shift lever. You could try replacing that sensor?

If you're not getting any O2 sensor codes (P0130 to P0139) then maybe it's actually a bad catalyst. Check your warranty book. I think the cat carries a much longer warranty then the rest of the car.