The plot sickens. truck sat outside for an hour. Customer goes to leave, truck in gear, foot on brake,abs light goes out. Wtf?
I think there is a backfeed introduced into the abs circuit. Guess its coming back. So its likely not the control module.
This is starting to sound a little bit like something that happened with my work suburban. When I went around a corner I'd get a bunch of lights including ABS but also traction control and more. I had put a lot of miles on that rig and what it ended up being was worn bearings in the rear axle. Crazy as that sounds rebuilding it fixed it. I guess there's a sensor and when the slop pulled one surface far enough away from the other it caused a "communication failure" and everything lit up. The first thing they had tried was the sensor, nope.