help with engine code

[03GXE30187]

'00 civic d16y8 at EX. P0420 catilyst below threshold (bank 1). can anyone help me with this and what I need to replace. I've already replaced o2 after cat. part stores are giving me the run-arounds

[Atlblkz06]

Sometimes the CEL will come back on after you replace the O2 sensor.

Give it a day or two after replacing the O2, it should go away.

Dont trust the computer to give you the right bank. I say just replace both of em. If one is dead, the other one cant be too far behind.

Good luck!

[03GXE30187]

oh and no mods

[03GXE30187]

o2 was not recenly replaced. it was replaced a while back. my girl just told me it has been on. I heard it may be the cat itself. is this correct?

[Atlblkz06]

Thats the worst case, yes. If the O2s are ok, then the system is not detecting a high enough change in the voltage between the pre-cat and post-cat O2 sensors.

I'm hoping its the sensors that are bad. If they're good, then its your cat - and thats mucho dinero.

[Tech5]

You need a cat! that is only how your going to fix it..Your car will cost you 400 OEM direct fit...Or 130 at a exhaust shop weld on!

[Tech5]

Wrong PO420 is his CATALYTIC CONVERTER IS BAD!!! That is only thing wrong!
Sometimes the CEL will come back on after you replace the O2 sensor.

Give it a day or two after replacing the O2, it should go away.

Dont trust the computer to give you the right bank. I say just replace both of em. If one is dead, the other one cant be too far behind.

Good luck!

[suprapower]

get your cat fixed!

[Barefoot]

its your cat. most bad o2 codes are caused do to a faulty cat. i had a ladies car come all 4 on her car was reading below .2 volts. i changed both cats and they all read perfect.

[turbob20]

yeah its the cat disrupting the flow. also be sure to take battery cableoff to clear codes when any attemp to fix somthing to see if it will clear or comes back on...

[mitch lab]

change the cat