99 Malibu ABS light

99 Malibu, both front hubs replaced in the last two years, brake fluid full, everything seems o.k.(brakes feel normal, ABS kicks in and acts normal, pads and calipers are good, no dragging, etc.) The issue is that after 15 to 20 minutes of driving, the ABS light comes on but there are no active or pending codes. It does it while just cruising along and remains on. Let it sit for awhile, no light. It threw a code last year when a speed sensor went but both sensors are fairly new now and no codes. Of course it does this right as it comes up for inspection. Ideas?

Check speed sensor wiring. I had this problem. Found squirrels nawed on my wire just enough to cause a short.