Which years had abs front and back? I've been running shorter tires on the back for a long time now, and never had the light come on. I always thought the ones with drum rear ends only had front abs.

 

I believe that the 97 still had the ABS IV system (as in previous years), which has a speed sensor on each front wheel, but just one sensor on the rear differential. Later years had sensors on all four wheels. Not positive, but I'm gonna say the four-wheel sensor system (ABS VI) may have started in 1998, since all models now had 4-wheel disc brakes.
If you have ABS (97 and older) you should see a little black module on the outside of your rear axle, top side, near the center section.

 

I have this ABS INOP issue too, my back axle is bent and it makes the light mad lol

 

I've got a 96, so I must only have wheel sensors in front. That would explain it.