Lots of possibles now. Thanks!
In the video, it looks like the whole front sensor does come out on the 2004 truck. Anyway it shows the wire cord leading away from the wheel so now I know which it is. I hope to poke at that and where it connects up in from each wheel to see if there is a loose connection that affects the ABS lamp. Maybe narrow it down to one wheel to direct the garage to.
Looks like the next brake job would be a good time to get the garage to check for the other ABS possibles. I can't do that kind of garage work myself.