ABS and Brake light always on

I have a 94 Prizm LSI. I bought it a few months ago and it drives and runs fine but the ABS and brake light never go off. When I first start it, the ABS ACTIVE lights up for a few seconds and then goes away. The ABS light never goes away. I have taken it to a shop and they could find nothing wrong with the brakes. The previous owner said the lights had been on since about 80k and now it has 147k miles on it. He also said he had slid into someone and barely tapped their bumper, so he believed the ABS did not work. Any thoughts on getting these two lights to shut off?