Hold on just a sec...my intent was not to be rude or to give an indication that I could not or would not help. I can understand how might have come across that way as I was very brief in my explanation and mainly directed you to the search function because this is one that others have recently described in great detail.

On a pre-ABS car, post wiring harness issue car, if your brakes are functioning normally and the light comes on it is because the differential switch has become "tripped" about 99% of the time. The main way to reset it if you are lucky is to mash the pedal realllllly hard in hopes of re-centering it.

If that does not work, you have to un-screw the the plastic do-hicky switch and recenter it yourself which I could not remember exactly how to do in the wee hours of the morning.

I did fail to remember that your car could have ABS in 1990. I which case even my very curt advise was misguided.

Again, not slight intended and I apologize that it came across that way.