94 PA, ABS light comes on at same time each day

[Mike_EX]

94 Park Ave, non-ultra 224K. I had a flat on the Left Rear, and had to drive on the mini-spare for a couple of days. I noticed that the ABS Light would come on after about 30 minutes of driving, usually in rush hour traffic, so some slow driving and some fast.
I got a new tire and put it on, but the strange case of the ABS light coming on after 30 minutes of Driving each day continues. Light goes off after the car is parked at work, or at night. I checked other threads on ABS, with lots of good info, but none with a 30-minute time frame problem.

Thanks for any and all info.