Service Engine Soon Light

I have a '97 S-10 2.2 4 cyl. with 66k miles. The "Service Engine Soon " light came on when driving home. How much of a immediate concern is this. Does it concern the emission system? (cad. converter going bad). Engine still runs fine with no appearent problems.

Go to an autoparts store and get the computer read. that will let you know what it is and then you can figure out how to fix it.