I got a CEL today, and my buddy that was drivin behind me noticed that there was black junk coming out of my exhaust when I would step on it, so I figure I am runnin ritch, maybe a bad O2 sensor?

I want to figure out the code, but I dont know how to check it myself?

I had a 94 civic and that was easy(little blue connector under the dash that you jump and it flashes the code out).

I have a B16 Swap in a 91 CRX. Can anyone help me out?