i was driving teh GF home yesterday and my CEL went on. it's a 97 civic DX. i just checked it this morning and it's throwing a P0420 "Catalyst System Efficiency Below Threshold". is the cat the culprit? btw, it smelt like rotten eggs after some driving.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ieatrice &raquo;</TD></TR><TR><TD CLASS="quote">i was driving teh GF home yesterday and my CEL went on. it's a 97 civic DX. i just checked it this morning and it's throwing a P0420 "Catalyst System Efficiency Below Threshold". is the cat the culprit? btw, it smelt like rotten eggs after some driving. </TD></TR></TABLE>
Yep, the catalytic convertor has kicked the bucket, bought the farm, flown the coop, **** the bed, up and died. Time for a new one. Just wait until you see the price of it . . .

 

I was all set to say "are you using a bosch o2 sensor?"
but the rotten eggs smell points to bad cat indeed

 

could be the cat OR more than likely the secondary O2 sensor has gone bad.

I thought rotten egg smell was the cat working super hard due to rich conditions... maybe I'm wrong.

 

2ndary o2 doesnt have any change in fuel consumption...its pretty much just there to monitor the cat itself

 

thanks HT.. always there to help and confirm!! aren't they like $600 new from honda? is there another brand that does the job for less?

 

you can get a stock cat brand new from honda for about $400, but there are many aftermarket companies out there that offer 50 state legal (except cali) bolt up replacement converters for around $100, it's up to you
here are some examples:
http://www.car-sound.com/
http://www.easterncatalytic.com/

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pdiggitydogg &raquo;</TD></TR><TR><TD CLASS="quote">2ndary o2 doesnt have any change in fuel consumption...its pretty much just there to monitor the cat itself</TD></TR></TABLE>
agreed, but again rotten eggs is bad cat or too much fuel? (or both)

OPs condition could be from bad primary and secondary O2... or wiring issue common to both.

Maybe it's my nature to question a bad cat. after 215k miles on the original engine/cat and no issues... All though I have not run one since my swap.