Why does it say check charging sytem it has a good alternator and new battery good

I'm having this same issue. Voltage at the battery with the ignition off, 12.2. Voltage when running varies, but is consistently 14.2 or more. New battery, new alternator, new belt, all fuses and relays checked, and even replaced the fusible link, which eliminated the no start issue. But the charging system light is still on. 5.4l, all new parts, voltage checking clear in all areas.