1997 dodge ram 2500 5.9 diesel

both of my lights, the brake light and the abs light, came on at the same time. the brakes work fine. what may have caused the lights to come on?
thanks.

A faulty brake light switch....do your brake lights work?

I have a 2000 cummins and had both lights come on too. Turns out my hydro boost was leaking the power steering fluid. Lost enough fluid before I realized and my rear brakes stopped working. Check your power steering resivoir. Once I filled it my brakes were fine but the lights stayed on. Probably a computer thing. May or may not be your issue. Just figured I'd let you know what my issue was and how I fixed it. Hope it helps