need help with my check engin light!!!!
 

i have a 99 civic ex and i swapped catalytc converters with my friend(same year and model). its a gutted cat so when i put it on my check engine light came on... my cat has an O2 sensor on it so i dont kow if thats the problem. i diconected my battery and that didnt work the light just went back on 2 days later... i tried the backup fuse... that didnt work... somone please help me... i like the cat... it gives me a lot of top end

Dang emissions stuff.. What code is it giving you.. In the Step By Step theres a how to on finding out if you need to.

Your computer is most likely throwing a code because the catalyst part of the catalytic converter is not there. When the cat is not gutted, the platinum coated screens normally in place cause the exhaust to heat up quite a bit. In turn, this heats up the oxygen sensor. The temperature of the sensor is not actually read by the computer. Instead, the sensor translates the temperature in to voltage which is communicated to the ECM. If the computer reads a voltage that is out of operating range, you get a CEL.

There are a few ways to remedy this. One is to use an OBD-I computer, which does not use a secondary oxygen sensor. Anotheris to wire in a simulator. These little gadgets send correct amounts of voltage to the ECM w/o the sensor even being in the cat. ZIP22 on ClubSi makes 'em as well as other companies. I'd contact ZIP first though, he's nice as can be and very helpful. One other option is to just put up w/ the CEL. It's been dyno-proven that the CEL caused by a secondary oxygen sensor does NOT hurt performance. Of course, the downfall to this is, if you really do have a problem, your CEL won't really be of any use to you. The same applies if you just remove the actual CEL bulb from the gauge cluster.

I HTH. :)