How do you reset the check engine light on a 1989 Mazda rx7 and what caused it to come on in the first place?

goto your local shop, or even better a quick lube (usually dont charge) and get them to run a scan.. it should be an OBD I sensor, not a II.. but any good shop will know that... they will tell you what set the light, and how to fix it, and they can turn the light off.... lataaaaaaaaaa