I put a DC 4-1 Header, 2.5 " High Fow Cat, Custom 2.5" Mid Section and a 5Zigen axle-back on my Civic and it ran great for awhile and then started throwing a CEL. I checked the code and it comes back as low-voltage to the 02 sensor. How do I fix this problem?

 

the high flow cat is your problem. since the 96-00 civics have 2 o2 sensors, the second one needs to see a change in air fuel to make sure the cat is running efficiently.

The fix is in this thread https://honda-tech.com/forums/honda-s2000-5/what-does-o2-simulator-consist-off-1251924/

 

true ^, you may need to run a anti-foul, if you for some reason lengthened the o2 harness you may not have used a good enough gauge wire too

 

I tried the non-fouler trick and resetting the computer but the light came back on? Is the sensor itself shot maybe?

 

It may very well be bad, some people have used 2 anti-fouls on each other but i would replace the o2 first and see

 

bump