The brake warning light turns on only while driving. It’s a jiggly on-off seems like a loose electrical sensor. Truck has ABS but is not the ABS light. Nothing wrong with the brakes and hydrolic fluid looks topped up normally. Should I be worried?
This is just a thought. I have no idea if it will do any good, but it did work on a car I once had. See if you can find the place where a wire is attached to the master cylinder. If you find it, clean and reseat the connection.
Often, the fluid LOOKS full, but really isn’t. Try adding, and you might be pleasantly surprised. Been there, done that!