You'd need to get the code for a place to start.
What you can do if you have some time to kill is pull out all 4 wheel speed sensors, and clean the ends of road grime/brake dust that accumulates on them. Take some brake wash spray, and spray into the bore of the sensor, while spinning the wheel at the same time, and that'll clean the pickup teeth as well.
You could also be looking at a bad hydraulic unit, relay, wiring, or control module as well. Guessing is pointless, really, you need to at least know what code is thrown.
I doubt it's an alternator issue.