Heres the situation, My check engine light came on about 2 months ago in my 98 honda civic dx hatch. and it was the code P0420 "Catalyst System Efficiency Below Threshold (bank 1)". I thought it was my cat so I bought some 4-2-1 headers. Keep in mind these headers have a spot for both o2 sensors(one before the cat, one after). Anyways so I thought I fixed my problem well turns out after I erased the code 30-50 miles later boom check engine light comes up again. So I guessed it was my o2 sensor.....WRONG. Samething happened, erased code, 30-50 miles later check engine light comes back on. The only thing I can think of now is I need an o2 simulator. Does anyone know where I can find an O2 Simulator and which o2 sensor does the simulator plug into, the one before where the cat was or after where it was? THANKS AGAIN FOR ALL THE HELP!

 

http://www.o2sensorsimulator.c...anced

 

do you have an o2 simulator from that company in your car?
P.S. I've been getting really shitty gas mileage, duh, Will this fix that problem too?

 

you said you have a DX, did you take off your cat mounted in the headers??? aftermarket headers do not have a catalyst in them, they are really meant for EX's

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dashskier540 &raquo;</TD></TR><TR><TD CLASS="quote"> P0420 "Catalyst System Efficiency Below Threshold (bank 1)". </TD></TR></TABLE>

bad cat, happended to me.. when u replace your cat, erase your ECU codes and problem will be fixed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dashskier540 &raquo;</TD></TR><TR><TD CLASS="quote"> Will this fix that problem too?</TD></TR></TABLE>

yes, same exact thing happended to me

 

i agree with "i need a new username" just get a new oem cat and erase your code call it a day. i hate those obd2 cars

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dashskier540 &raquo;</TD></TR><TR><TD CLASS="quote">98 honda civic dx hatch</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dashskier540 &raquo;</TD></TR><TR><TD CLASS="quote"> I thought it was my cat so I bought some 4-2-1 headers. Keep in mind these headers have a spot for both o2 sensors(one before the cat, one after). </TD></TR></TABLE>

 

'I need a new username,' I dont have a cat anymore hence the two bungs in my new 4-2-1 headers. It completely bypasses a cat and goes right to my catback exhaust. So sorry problem not solved.... thanks for all your posts though!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dashskier540 &raquo;</TD></TR><TR><TD CLASS="quote">It completely bypasses a cat and goes right to my catback exhaust. </TD></TR></TABLE>

thats ur problem...