John,
We had a similar experience last spring after a stop in Grants Pass for a tire wear problem. We were referred to Eugene for a frame straightening and as I got out on the freeway heading for Eugene I noticed the ABS light was on. Called the Grants Pass folks who stated it wasn't due to the front wheels being taken off, brakes checked, front end aligned, etc.
Pulled into the truck frame shop in Eugene and mentioned it to the service manager who knew immediately what the problem was, fixed it quickly at no charge.
The Grants pass folks had not reset the ABS sensors on the wheels. Apparently they have to be at a certain spot or the system defaults to the ABS light on. Simple fix, disappointing cause.
Perhaps that is all your problem is........ Mike