got a 1996 chevy blazer and service engine soon light came on and it drives
fine no leaks
and has plent of high octain gas in it. If anyone has a answer to my
question please email me. What could it be and How to reset the light to
turn it off?

That's not a lot of info to go on, best bet is to take it to a parts
store that will scan for free(i know autozone does this) they will tell
you what the code is. Then buy yourself a chiltons service manual for
the truck, or better yet go to helminc.com and get a factory service
manual(expensive but worth every penny). Either of these manuals will
have a diagnostic chart for each trouble code, ie check resistance from
here to here if less than... replace....